I think, if you have the money, the 90 days is well worth it, even if not always necessary. It's always interesting to spot things you didn't, upon second and third looks at something, and, even after you've exploited a lab box, sometimes, you'll find other ways (or better ways) of accomplishing the same things, as well as being able to try different tools against the lab, to see how the behave, how quickly and accurately they report findings, etc. It's a good test ground, as well as a training ground.
Good luck, and let us know how you do!
Thanks guys.
I wish I could afford the 90 day lab, but unfortunately, not at the moment.