I wind up buying basses I think I'll like, and then selling them when I don't care for them that much. Hence, I only have 5, and one is on the way out soon (have to replace a pot). I need some more. Going to the guitar show next week looking for a couple of things... ;D
Just buy what you want and can afford. Buy it right so you can sell it without losing money. If you feel like you have too many, sell some. If you feel like you don't have enough, buy some.
As far as investing your money, there are worse investments than a nice bass. If you have credit cards with balances and high interest, better to pay those off first, and you'll have more money for basses!
I totally agree. There is an "educational" aspect of GAS. I've discovered that if you want to learn about something, the fastest and easiest way to do that is to get one, find someone who already knows what you want to learn, and have them show you. After you live with whatever it is for a while you will have a great deal of detail knowledge of it.
At that point you can ask yourself: "Am I going to do this in the future?" If the answer is "yes" or even "probably" you keep the bass. If the answer is "No, never!" you sell the bass and hopefully you were smart enough when you bought it that your "lessons" will be somewhere between cheap and free! Even if you sell the bass you get to keep what you've learned!