Steve makes a good point - 6 weeks definitely stretches the resources of us non-students, 8 weeks (contrary to my original post above) would make it worse.
The spoiler text in Billfred's post* has a good is a in there: a 5 week build season, prefaced by a 1 week design season.
It's been said before, FIRST isn't advanced shop class, witness the teams whose student design is implemented by professional machinists, perfectly within the rules AND spirit of FIRST. It's about the design, and the finer points of fabrication (i.e., making it work), not running a milling machine or band saw. **
Keeping at 6 weeks, but putting an bigger emphasis on the design process, might pay some good benefits. (Alternative: Give an award for a well-documented design - submitted in week 2!)
Don
* Not sure where that spoiler text is from, didn't see it in a previous post, so I assume Billfred wrote it but then hid it. OK. (cool BBcode feature I wasn't aware of, too!)
** Our team does let the students do the fabrication as well, even though us mentors would like to play with the tools instead

I personally disagree with the professionally-built robots. But, this practice does not appear to interfere with the mission of FIRST, and so I really don't argue the point at all.