I'm pretty much in the same boat. I've never bought any basses as an investment, although I always try to think of what the resale value might be if I ever did sell. The Newport may be the exception, but that will take a couple years to pan out. I'm thinking of doing a nice black refin, and then sell it in a couple years. I'm still playing it occasionally in the meantime. I would probably come close to breaking even if I ever had to sell everything outright, with a few basses making a little profit.
The Columbus Guitar Show is coming up. It will be interesting to see how many people come to sell, and what the prices are like. My guess is that the show will be light, not much vintage will get sold that's older than 20 years, and the new stuff brought in by the Low End will have some modest, but bigger, discounts over normal pricing.