Scotty, I recently bought. 2013 Toyota Sienna xle awd with close to 140k miles on it. Its been serviced by the Toyota dealership up until I purchased it. The service records online back that all up. I'm planning to use the van to tour the US if this Covid ever gets in check.

I have plans to do a lot of services to it. Changing all the fluids & filters; air, oil, brake, coolant, transaxle, differential and doing a drain and fill on the transmission. The vehicle runs fine. Am I crazy for thinking while doing all this to change the water pump, thermostat, belts & hoses, idler pulley, belt tensioner and the spark plugs? Or should I leave these things alone until they go? Toyota says most of these things are lifetime components, I've always kind of thought 120k is what Toyota means by lifetime as that's when their warranty ends. 

Aside which brands should I be looking at to get original equipment quality for these components if I do replace them with out over paying at the dealer? Rock Auto lists several brands for almost every component I listed. Including Denso, Aisin, Gates, Continental, AC Delco and a few others 

I've read on some forums of people who have never changed the spark plugs and they have 300k others that have said they changed them at 200k and they still looked fine. Your opinion? Sorry for being so long but I wanted to be as detailed as possible and not generalize my question to take advantage of your expertise. Thank You for your time and love your channel.