Q: 1996 honda accord 210k runs great.is it true to wait till something is wrong, to take it to a mechanic?

I recently bought a 1996 honda accord ex at 210k and as of now everything runs very well. The start of the engine is strong and smooth and the engine is quiet. The car was maintained by a family mechanic prior to me buying it, so there are no service records. I made minor repairs like oil change, replaced spark plugs, replaced tires plus alignment and breaks. The mechanic told me the car runs well but followed with that parts are worn and then tagged on a hefty price tag to replace them. My first question is...is it true to not replace anything on a car until something is actually wrong with the car? My second question....what inspection should i get to find out the overall health of the car? I would prefer a full inspection from top to bottom, so i can get a baseline of the car...does that exist? Thankyou

My car has 210000 miles.
My car has an automatic transmission.