If consumables: ie Tyres, pads, oil and filter servicing etc or general service records were poor there's no doubt i'd walk away from the sale. Even if you could perhaps notice any CVJ's knocking, bottom ball joints etc on a test drive; i think i'd do the same. All a sign of being poorly looked after imo. And perhaps a sign of the life its lived.
I mean when you see cars for sale and they go on and on in their advert about some minor problem that "only costs £50, but they havn't had time to do it"......what does this tell you about the owner ? !
BUT: In terms of the belt change - if everything else checked out, if the car was good and if there was room in the price - i personally would buy one where the belts were about due or slightly overdue - purely for the peace of mind of then owning a car where just about one of the biggest jobs possible on these cars was going to be done at a garage of my choice, giving me 5 years peace of mind.