I have 4 basses, but only wind up playing 2 of them regularly. What's the best advice for keeping the other 2 in storage? Currently they're upright, in the case, with strings de-tuned about two whole steps. Climate and humidity are not a problem. Should I NOT be de-tuning them, or is that a good idea? Should I NOT be storing them upright? Should they be lying down in cases, ON STRINGS (to place pressure on neck) or on their back (which places the WRONG pressure on the neck) Advice? Thoughts? They two basses in storage are a '69 P-bass and '72 Jazz bass, so I'm concerned about the necks most of all. Any bona-fide repair guys or gals out there who know the actual answer to this question?