mothwentbad: I think the later gear doesn't drop as often. Boss rooms (marked with ?), like the giant skeletons or the enormous spinning painting of death, tend to almost always drop something unless all the gear of that area's tier is already acquired (I think). So you might clear an entire area and just not get any blueprints. But if you die in The Maya fighting a Sallos, it might be worth a lockdown just to get another shot at it.

I'm only 30, but I hope it works out for you at your advanced age. X-D