I feel that cross training is a good thing. People always ask how it can be done, time wise. Very easily. Whats the rush? IMO, the goal shouldn't be to rack up 30 different arts, to pad your resume, but instead to just learn.
this is a really good point. i visited an mma gym that claimed to offer around a dozen styles. judo, silat, boxing, muay thai, bjj, & several chinese styles. they had one instructor, who was around my age (about 30). my point is i was a little suspicious that he was qualified to teach all of these things, let alone combine them all into a cohesive fighting style as promised.