Having a consistently low income, I played the first three generations of pokemon games... at least six times. Each. I have nearly exhausted the series, but I still play one of each new gen game at least once. However, if the next set doesn't have any noticeable innovation, it may be the first one I pass over.
Also, having played Fallout 1 and 2 twice each in the space of two months after getting them, my only incentive not to play them again is that I don't want to wear them out. Playing those games with a different character build feels like a unique experience each time, so I feel like I will revisit them quite a bit.