This is for motorhomes. I have a feeling that most "RV" are towables, i.e. trailers and 5-ers. Maybe in rental sector it's different.
For those other types of RV life is measured in years only, and can be several decades, subject to fridge repairs/replacement and roof recoating (~12-15 years either one). Mostly, depends on climate - can develop bad leak in under a year and destroy the whole box if left unattended. Or can outlast the owner.
Many things need to be fixed/upgraded from the day one, some are more important, some less, too many to list. Motorhome innards (not the engine) often fall in the same category - need upgrades straight from the dealer's lot, though MH owners are usually less enthusiastic about DIY upgrades than towables owners.