OMg my coworker does this too. I hate going out to lunch as a group because she will chat the whole time and then when we are all done and ready to go she still has most of her food on the table and still has to eat.
And people wonder why I am an introvert.
I think most folks don’t intend to be that kind of old person. It just happens. Your brain changes, your social situation changes, and someday - without even noticing - you become the kind of old person who rambles on and on, responding to minor inquiries with vast sagas.
My own parents, in their old age, have developed the neuroses that seem to be very typical of the elderly. They definitely weren’t like this 20/30/40 years ago, and I doubt that this is what they intended to become. It just happens. 
No! I HAVE SPOKEN. I will lose all filters and tell the idiot at the Costco he is an idiot; why did he put the eggs and bread and chips all in one bag with the chips on the bottom? Dumbass. When people are rude to me I will be rude right back. I will be a bitchy old lady.
My SO says it’s going to be such a pleasure living with me. 
Ugh, dear hubby does something similar to this. If I miss a line of dialog in a tv show (because the interstitial music is so loud it drowns out the dialog, but that’s a peeve for another thread), and I ask him what was said, he’ll repeat back the entire dialog from some random, but way too early, point. I’ve tried cueing him for the exact part I missed, because sometimes I just missed a key word. For example:
me: He said “I’ll get you a … what?”
hubby: she said “whatever, blah blah blah” and then he said “I’ll get you a cookie” and then she said “more blah blah”…
or
me: what did he say just after “I’ll get you”?
hubby: she said “whatever, blah blah blah” and then he said “I’ll get you a cookie” and then she said “more blah blah”…
I’ve straight up told him that if I needed a court reporter, I’d hire one, but he still does this.
I encounter pretty much the opposite problem with some family members, except relating to real life rather than TV. They don’t repeat enough of what they said rather than too much.
Them: Would you put the unintelligible in the dishwasher.
Me: What?
Them: (Exasperated) The dishwasher!
Admittedly, I didn’t say which part I didn’t hear, but why do they assume it was only the last part?
Yeah, I think it’s something that just starts happening when folks get to a certain age. My mom has always been loquacious, but lately it is getting worse. I ended up having a 20 minute conversation on the phone last night in response to my question, “Are you coming down Wednesday evening or Thursday morning?” It’s frustrating, but I really try had not to get to frustrated. After all, she’s my mom.
This is hilarious! Grandpa Simpson’s story was the first thing I thought of when I read the OP.
I believe it’s loneliness more than age. If you’re naturally talkative, and don’t see anyone all day except someone in health care, you’re going to run off the deep end when you finally see somebody.
When my mom does this and I start to cut her off, I just think about the day she won’t be here anymore. When I would give anything to hear one of her rambling answers again. I just let her talk and I listen.
I do the same thing, or even say, “Stop talking now.” It’s usually at work in response to a computer problem. Then I say, “What is the computer doing that you don’t want it to, or what is it NOT doing that you DO want it to do?”
I did tend to ramble on and on, then I found this new age supplement that improves concentration, with hardly any side effects, and can you believe those drug ads on TV with all their side effects? It sounds worse than the psoriasis, which is what my Aunt Mary had, which was so bad she could hardly ever leave the house and used to frighten the mailman, which reminds me that they’re going to get rid of Saturday deliveries and I can’t wait until Monday to see the circulars 'cause there’s going to be a big sale at Walmart. And did I tell you about the time I was a Walmart greeter and we all tackled a shoplifter and made him give back the flat screen TV he was hiding under his shirt? Yes, with the old TVs you never got away with that, in fact my Uncle Phil got a terrible hernia just moving the Magnavox into his living room.
Where are you going?
That’s because you weren’t here in 2000. I was a mere lad of forty-six, hardly elderly, when I discovered this board. I was checking on the latest Straight Dope column and saw there was a message board, too, and it didn’t consist entirely of trolls, unlike everywhere else on the internet. But one thing stuck out: in a thread about The Simpsons somebody was wrong. I didn’t know that it was already a meme for someone to stay up late to correct somebody; I don’t think the now-classic XKCD cartoon had been drawn yet (xkcd: Duty Calls). Have you noticed how often he parodies people like us? While there has been a reference or two to the SDMB and Cecil, I don’t think he–what’s his name? Something like Russell? No, I remember; it’s Randall–is a regular poster here. Anyway, much of my Simpsons knowledge can be blamed on my children because, when they were taking their bottles before bed–Wife didn’t even try breastfeeding twins, no matter what those crazy zealots want–they liked to watch cartoons. Any cartoons, so they developed a taste for The Simpsons, and I saw the first couple of seasons over and over again. So when I saw that someone was wrong on the internet I had to join, and that’s when I started my long, rambling, stream-of-consciousness posts. Sometimes I saw how long I could go, how convoluted the tale, without using a full stop, but it made people mad so I stopped.
When you are an old woman you shall wear purple
With a red hat that doesn’t go, and doesn’t suit you…
Well, being the conservative candidate I tend to drone on and on and on and on and on without letting anyone else get a word in edgewise until I start to froth at the mouth and fall over backwards…WHOOOOOAA!
My wife gives details that I see as totally irrelevant, taking 5 minutes to say what I probably take 30 seconds to spit out. She knows that I’ll zone out for 4:30 and scan for the gist of what she’s saying.
Because that’s how they used to teach students to write papers (both high school and college). Supporting info, supporting info, supporting info, THEN your statement.
In business, they tell you to make your point or assertion, the follow it with supporting information and/or examples. That’s what most people want these days (including me).
A friend of mine got pulled over in rural Colorado many years ago. He was on a trip to visit a long distance girlfriend, and that got the conversation to relationships. The trooper spent more than an hour rambling about his troubled marriage. My pal didn’t say a word because, hey, if the cop stops talking he’ll just get back to writing the ticket. At the end of an hour the cop just let him go.
Yeah, sometimes you just need to vent.
It’s the beard.
Why wait? I tell the grocery packers now that I really don’t want the chips under the 80 cans of cat food.
Oh, I do too. In the future I will just add the addendum: dumbass.