The thing I like about branching and specializing crafting classes is that it keeps people from maxing out all crafting classes without eliminating the sense of "I could do more"

The XI system people maxed out as far as they could (and even would use multiple characters to get around it), but then the crafting 'content' (I use the term loosely) ran out.

If it take 36 years to achieve mastery in all crafting specializations, a person that enjoys continually progressing can just keep doing so. I'm not sure, since I didn't play EVE, but it's my understanding that EVE uses a similar skill-branching system. I know that the MMO Ryzom did (not that is necessarily a great endorsement, since that game was eclipsed by other 'theme-park' MMOs released at the same time).