Most of the cars I get are ~200k miles and for some I have used about 1/3 to 1/2 bottle of
Rislone Engine Treatment when nearing an oil change interval, say within a week or 200 miles. That's about as much of "flush" as I deem would be necessary for most of the vehicles I have being they were regularly serviced and didn't have issues of neglect for the most part.
The 2005 Camry you describe at ~ 80k miles should be fine with no flush and switching back to OEM spec 5w30. If the oil has been looking excessively dirty or low prior to the first oil change, than do another oil change in a month or ~ 1k miles. Otherwise I'd go to about 4k miles oil change interval. Checking the level about every week to begin with and then every 3 to 5 weeks if all seem good and the level stays on the high mark.
I have the 2005 Camry, like yours with with the 2.4L 4cylinder engine and 227k miles and it gets an oil change every year being my mileage would be less than 4k miles in a year. I have only found the oil level less than 1/4 quart below the add mark. I just added that amount to bring it back up to the full mark on the dipstick. Right now I attribute some of the oil loss to the timing chain tensioner having a drip, being I changed it out with a new gasket and there hasn't yet been a new drip forming when it's parked. The other likely place oil could leak is the timing chain cover.
Water pump can be an issue to watch on these, and I once had the thermostat stick shut and it started slightly overheating but I got it shut off and cooled down enough to drive over to my parents house and change the thermostat with no issues. The thermostat housing gasket needs to be thick enough to keep coolant from leaking, the
AISIN THP101 is the one I found that works, not sure about other aftermarket gaskets but I had trouble with a small drip until I figured this out.
Now if you can change the transmission fluid and it isn't all rusted out, it should last you a long time. The one other thing is the power steering fluid because Toyota's can have a problem with leaks, although I changed mine out with high mileage transmission fluid with seal conditioners, and had good results, I think a lot of people got talked into replacing the power steering rack because of a leak, at a large expense and may be not necessary. I also changed 2 power steering boots that were torn, but never had to replace the rack.
Spark plug coils are another nice resource to have a spare or 2. Just had a buddy get stuck with a tow/fix charge on this problem, though it wasn't a Toyota, I think the bill was probably more than $500 and something that can be avoided if the fix is as easy as changing a coil. I also have a spare starter, alternator and being this is drive by wire I am working on getting the spare gas pedal actuator and throttle body, either one of these failing could also leave you with a tow/fix charge.
Which reminds me of 1 last fix, the steering wheel clunk if you rock it back and forth. At the interior steering column/shaft, at the bottom the is a gear spline that goes into a collar, with a needle adapter on the grease gun I squeezed some grease into the fitting and the clunk stopped, some have also taken apart this joint to grease it but I didn't find that necessary.
Nice car, I once rented the 2016 Camry and the seat and the ride was so stiff I could only think my 2005 rides better that this one, and it's easier to get in and out of. I think they went to a more 'sporty' ride to appeal to ...a buyer, and I'd prefer a more comfortable ride. The 2005 has a slightly bigger body and sits up a little higher is probably what I attribute to some of my preferred characteristics.
Being edit is still an option, throttle body cleaning. At your 80k miles, it is probably not a high priority, when I got my 2005 Camry at 205k miles it needed cleaning. I also had a 1996 Camry that had the throttle stick open, and hence forth cleaning it solved the issue.