Also depends on what you consider keep going to be defined by and what rules you are using.
If you have a 10 team, 8 leeper league for instance, you are probably looking at 3-5 years before you will either lose a lot of owners that will be difficult to replace or you will have a top heavy stratification. That meaning that 4 or 5 teams have very good players, a couple have OK keepers and 3 or 4 are basically inept and hopelessly ouut of contention. It is hard to get a new owner to take over a team of 8 keepers where he has no one (or only 1 or 2) players worth squat. At that point, you either have to abandon the league, cut the hopeless owners a bone by lettig them play for free or on the cheap (assuming a money league) or cut down the keeper count to 4 or so to re-balance the league out. Technically this may be the same league, but in reality it is a sizeable re-alignment and quite different.