Thinking more about this, I've revived 3 "field cars" and one "barn find", so far.
1) My first car could have towed this sailboat+trailer! It was a huge BOF American sedan: 1964 Pontiac Catalina 4D hardtop with a 389 V8. It had "ran-when-parked" status - for an unknown number of years - when I bought it & fixed it up.
(Not the actual car)
2) The MPGiata was parked beside a hedgerow out in the country for 2.x years, essentially abandoned by its previous owner.
3) The ForkenSwift (Geo Metro) was also given up for dead, parked in someone's side yard, though it had been sitting for less than a year I think.
4) The Firefly was parked the longest, but was the easiest to "revive". It was parked for 7 years, but inside a garage, and all it needed was a new battery.