Don't think I've ever owned more than 4 at any one time, and I used to feel that I needed to cover all occasions. Realistically, I've always found myself favouring one over the others and now I've got back into playing a 5, I don't really feel the need to keep 4's and 5's as I can do everything and more on a 5 that I can do on a 4. I'm aiming to sell my other Sandberg Basic 4 in order to buy a brand new Basic Ken Taylor 5 in whatever finish I decide (if I ever decide!), and just have the two of those. I find them immensely comfortable and easy to play (which is always the main thing for me), and there are more than enough tones available to cover any situation. I'm not really that vain when it comes to basses, but I'm glad it's not just another Fender-a-like!
I'll always keep my my modded RBX270 as it makes a good backup, and it's nice to have a knockabout bass permanently in the living room that I don't mind the kids getting their grubby mitts on!