You’re doing just fine..

You’ll find all the intervals in your owner’s manual.

For things like the water pump, alternator, etc, replace when they start showing symptoms of imminent failure.

For engine oil, I would change every 5,000 miles.  For transmission, I would go every 40,000-50,000 miles (drain and fill with filter change) (that is more aggressive than the manual says but you’re not going to have regrets doing it more often.)

Also a good resource (even if you don’t do the maintenance/services yourself, you can at least be aware of what is involved) see videos below from Toyota Master Mechanic The Car Care Nut:

https://m.youtube.com/channel/UCEKt2bUDBoRUw3wpPpDOUaA

for engine oil id change every 5k with full synth regardless if highway or not. i personally dont like dealer bulk oil i buy mobil 1 extended never had problems.

when i bought my 2010 honda accord 60k miles used, i drain and filled all fluids regardless and did trans twice. do not flush anything. just drain n fill

use oem toyota dealer fluid for all its the same price as other name brand, better stay safe.

you dont know what first owner did. just buy the coolant, power steering, brake fluid, trans, spark plugs NGK. my mechanic changed all my fluids and plugs for 100$

for air filter every 15k-20k miles. if you drive alot a KN box filter is probably worth it 

after you do it, you can change coolant everfy 80k, power steering every 50k, brakes 2 years or so, transmission id do it every 30k miles for the best longevity, plugs every 80k/4 yrs

but for the oil change do it 5k mile max

Thanks, guys. I just bought new tires and they tried to upsell me on a new serpentine belt. I asked 2-people. One said it could go 125,000 or more. Another said I should replace at 60,000, but, that's manufacturer recommended on a lot of belts, maybe 10-years ago. I had someone do a visual inspection who is a mechanic and he said even without symptoms, you can't tell by looking at it. You have to check some measurements or something and cross reference a manual. I guess to keep it simple, when I hit 90,000, it wouldn't be a bad idea to change it?

The coolant is original, but, I just watched a Scotty video this weekend and he said some of the modern cars have coolant that can go 5-7 years? On the other hand, not replacing it can cause problems if the coolant is breaking down. Changing the coolant at the Toyota Dealer is $150. Doing a Brake Fluid Flush is $100. The serpentine belt is around $225. Then, there's a fuel injector cleaner they do for another $100. With nothing wrong with the vehicle, I could easily drop close to $1000 on all these pre-problem maintenance things, so, a consumer gets caught up in which one should I do, which one should I wait on, which one should I skip and manufacturer recommended maintenance schedule is often vague.

On mine, it says "inspect" "inspect" on a lot of things every 15,000 miles and then who do you trust? The guy at Toyota who said I should do the serpentine belt did not do measurements or anything. He opened the hood and looked at it as a "service advisor." A friend of mine who won't work on my car, but, has worked for Infiniti as a mechanic told me that visual inspection is not enough to determine the state of my serpentine belt. I go to the dealer because where I live it's hard to find a trusted mechanic or if you do, one that knows what he's doing. I've seen too many people burned and wasting money on guesswork, with mechanics experimenting and charging for unnecessary repairs until they correctly diagnose by trial and error, and that's if they are somewhat honest and not just ripping you off. 

I guess sparkplugs should be done soon, too? By 100,000? I'm a guy that doesn't own a socket set. Looks easy. I just don't want to mess anything up and I'm willing to pay a professional. But, when Scotty shows how easy it is, I'm afraid to ask what they are going to charge for that. They'll bundle it as some kind of comprehensive 100k maintenance service, pop in a new air filter and stuff and who knows what they will charge. Speaking of air filters, I used to change air filters every other oil change on my older cars. On this Camry, I've only changed it every 30,000. What's your thoughts on changing air filter and cabin a/c filter? Every time I go for service, they want to change them and they are not as cheap as on my older cars. I used to unscrew and put air filters in myself. The cabin a/c filter should take 5-minutes, too, from what I understand, but, it is inside behind the glovebox or something and I'm not sure about doing that one myself. But, on any AC, I would guess it's important, but, how often? I'm in Florida and run the AC all the time.

Thanks for everyone's feedback