that is really a bad case to site for needing to keep all your receipts and such.
It is a used car someone bought trusting the person they bought it from to have done all the maintenance.

I know I wouldn't take someone's word for it. I would verify or change parts right after I bought it if it was on the boarder for having it done.

as for needing receipts, the only example he gave that might make me pause was if the car had a known sludging problem, and I needed to prove it. But even then, I think that is a bit rare for someone that actually maintains their car and checks the oil etc...