I consider this to be poor advice. There is a reason the belt has a recommended change interval.
The down side is if the belt breaks, the cost is way way higher than if you just went ahead and replaced it.
Thanks, zenith.
The priciest repair was the timing sensor. IIRC, that may have been around $3-400. Each of the other 3 were under $200 apiece. The total bill was just a hair over $900.
The mechanic did say everything other than the MAF could wait. He said doing all the repairs was a lengthy job, going to take a couple of hours. So I understood he wasn’t going to simply be replacing a fuse or downloading something into an on-board computer.
Plus, they cleaned it up real nice both outside and in! 
for my wife I brought home a quote for AAA, if that would give her peace of mind. @ $65 a year for the both of us. A lot cheaper than a new car!
When I was young, an old car was something that you could tinker with yourself pretty much with a set of wrenches and a couple of screwdrivers. But those days are long gone. Keeping these cars as they mature definitely goes well with my dislike for so much of what I consider our disposable culture.
TW - these repairs were on a 2003 Matrix 4cyl, not the Sienna - which I believe is a 2000. I don’t have the invoice in front of me, so it is possible I simply wrote one or the other items down wrong, but I don’t believe I did.
A couple of the items had 2 or 3 things specified under each. For example, I believe under “belt tensioner” it separately listed “belt.” I’ll check the invoice when I get home, tho, and let you know if it sheds any further light.
The only thing I can suggest is to ask the mechanic to cite(make sure you point at each line item and yell Cite! 
) his sources for the part prices. I know my mechanic always tells me exactly where he is getting parts from at the price he quotes (usually Worldpac), and will advise me on any cheaper sources that may exist (Dealer, driving across the border to the US, wreckers, Factories in China, etc) and the corresponding risks, shipping costs, etc. Usually, he gets better prices than me, but not always.
Cars built within the last 20-25 years vs. the “classics” are a real “on the one hand, on the other hand” situation.
On the one hand, there’s no every 6 months ignition points change, no frequent tinkerings with the carb and automatic choke. The car always starts in cold weather; almost never “floods” ,diluting the oil with raw gas that gets past the rings, and pulling down the battery as you try to “unload” the fuel system.
On the other hand, once the car is 5-8 years old, all the money you saved not having to do tuneups, changing oil less frequently, etc,. is needed to replace stuff that’s not often user-replaceable. Your first $1K repair shocker is the price you pay for 5-8 years of “just fill her up , change the oil 2-3 times a year, and go”.
Personally, I’m getting too old to constantly putter under a hood and to have to keep AAA on speed dial every winter. Good Old Days, Bah Humbug!
The best 5-8 year-old used car is one you’ve owned 5-8 years and that you KNOW has had all the stuff that wears out @ 5-8 years taken care of. Buying someone else’s 5-8 year-old car is a real crapshoot as to whether you’re going to go 2 weeks or two years before you’re first $1K bill hits.
A lot of young people who have little cash, but good credit are probably better off buying a brand-new car, since for at least 5 years there’ll be no surprises. Just monthly payments and routine maintenance for the most part. And anything serious will be under warranty.
Unless, of course, the young person has a “parent certified” 5-8 year old car that never failed Mom and Dad , but that they’re just tired of.