Thank you so much for that.
Oh, Lord, I’m so sorry for your grief! I agree with “nearwildheaven”. When you feel the time has come, then it has. 
Thelma, I really have to compliment you on how well you have assessed this, and how clearly you are viewing this horribly challenging situation. I don’t know that I’ve ever seen it expressed better. It is really tough - but the one thing you can be certain of is that you are making a well reasoned decision that is best for you and your pup. Can’t imagine anything else mattering. Good on you!
What I found most telling were your comments that you could do it today, and not beat yourself up thinking it was too soon, and your thoughts that maybe you let your previous dog hang on too long. It is almost lucky when there is an acute change that signals, “This is THE DAY!” But that generally isn’t the case. Keep an eye on the factors you describe. The falling, lack of mobility, lack of enjoyment, and incontinence are the factors I would personally key in on. In addition to appetite. If more than one of those started getting a lot worse… But right now you are in the range where you acknowledge it could go either way. So enjoy this time as best you can, while as best you can preparing yourself for the eventuality.
Frame of reference - we never got more than 12 yrs out of any of our big dogs, so I’m jealous at the 15-16. Our current 2-yr-old mutt is smaller, and we are hopping we might crack the 12 year barrier.
Thanks for your close reading of my comments. I’ll be watching her like a hawk.
Better than as a vulture! 
(hoping even black humor can help in challenging times!)
I’m just … so sorry, ThelmaLou.
I’ve seen a couple of your threads/posts about Sweetie, and can say without hesitation that you love her dearly and take excellent care of her.
Which never stops them from getting old on us, does it ?
Whenever I read one of these threads, my yellow lab (that’s him in my avatar) seems to know it. He’d want me to send his love your (and Sweetie’s) way.
As I send mine.
She’s a beautiful dog.
Y’all are making me cry… In a good way…
Sweetie is looking pretty good this morning. She got up with me around 6:30 and immediately went looking for her brekkies. In her bowl I put some pot roast, beefy dog food with some flax meal mixed in, rotisserie chicken, a hard-cooked egg sliced up, and a heaping tablespoon of cottage cheese. She promptly ate about half of it. YES! She will eat the rest of it over the course of the day (and may even want more chicken). I also put out a bowl of salmon with green-lipped mussel powder mixed in. She may or may not eat any of that.
Based on what @kayaker said above about hair loss, followed by my own research, I’ve decided to stop the Carprovet. Hair loss is a known side effect of NSAIDs, even in people. She’s also on tramadol and gabapentin so I don’t think dropping it will be a problem.
Here’s how to make the slippery floor mostly navigable.
You are a good person.
It’s hard to tell from that picture – does she need her claws clipped? I think overly-long claws can often make walking more difficult; and old dogs usually don’t wear them down enough on their own.
Yeah, she does need them trimmed. I’ve never done it, and getting her in the car to take her to the vet is very stressful for both of us, but especially her. Any ideas?
Some dogs will tolerate the use of a dremel tool to grind away excess nail tissue.
Are(n’t) you in San Antonio ?
Or … wherever you are. May be worth the $.
I have used mobile groomers in the past. The cost isn’t an issue. I could call the one I used to use…
I would not feel competent to give that a try.
Of course she is! She was reading over your shoulder as you started this thread!
“I’m not dead yet!” 
Enjoy the time you have left with her. Be sure you don’t fall into the trap I did 3 dogs ago, where I over-focussed on the limited amount of time he appeared happy - lying in the sun, while failing to appreciate how much discomfort he was really experiencing most of the time.
Good advice.
They make scissors specifically for the purpose, shaped to hold the claw.
Some examples here:
The tricky part, however, is making sure you’re not cutting down into the quick, which would hit both nerve endings and blood vessels. That’s fairly easy to see on light colored claws, but is difficult on dark ones. If you can get a professional to come to the house, and can afford the cost, it might well be worth it.
I’ve read that if you go too long without trimming the nails the blood vessels can extend down into the nail, so that makes it even harder to see. I did just leave a message with a mobile groomer.
Aside… untrimmed cat’s claws are really a nuisance, especially if the cat in question likes to crawl up on you when you’re in your jammies or something lightweight and make biscuits. I had one cat who would let me trim his claws. Okay, full disclosure: he would sit on the arm of the sofa next to me and let me stroke his paws while we (I?) watched TV. Damn, I need a Social Life. One day, I thought, “Maybe he’ll let me…” and sure enough I could trim all of his front claws during this little love fest.