I don't get what age has to do with anything in all honesty, like Odysseus said, there are some god-awful old Doms who don't know anything about being a Dom...

I have to say that within my local bdsm community, there are some pretty amazing Dom/mes from the <25 crowd, no joke there. I think it's because we have such amazing older Dom/mes to help mentor them.

Anyways, "how many is too many" all depends on the people involved and it's all circumstantial. Like Dom/mes will play with other people but they may not be 'regular partners'