I think that the number of ejections theory comes from the days when the medics were lacking some of the tools to investigate the potential damage that they now have. Old seats BIG bang, new seats longer periods with high g loads, different sorts of injuries from then compared with now. Docs were inclined to err on the side of safety, makes sense to say "after two big bangs no more flying for you Jim Lad" if you don't have the MRI or Cat scans to see what has gone on.
If there is no sign of damage and the docs can't find a reason to "protect" you from yourself them there is no "rule" to be inforced as far as I know.
If you read the appendix to Sir James Martin's biography I think the stats are 6000+ ejections, 250 double ejectees, 20 triples and a couple of 4 timers. Mind you this is only MB seats, would be interesting to see stats from FSU and other manufacturers.
Me, I called it quits after two.......
Tarnished