I just got a 45# K-mag this spring, and it is a GREAT little bow. I confess to shooting it more than anything else right now.
I'd also love to pass it on when the time comes, but until then I'm going to keep it strung and shoot it often. If it doesn't make it into my kid's hands (I'm thirty and just starting to expect babies), I'll make sure they get a K-mag of their own.
Watch for twist, stress lines, or delams, just like any other (newer) bow. Keep it out of the corner, the attic, and hot cars. That's it. And shoot it regularly. That's what I'm gonna do. Anybody else feel free to correct me, but I've heard nothing but good stuff about the longevity of the K-mag, as long as it isn't grossly abused.
-Charlie