Yes, anyone with more than 1 bass can totally relate to your dilemma. I own 11 basses (yes, it started with one) and the way it is for me, i wanted to have variety while i was developing a style, that is not restricted to one bass only. However, you can master one specific instrument if, that what you desire.
Imagine, if you are a Ninja, then you don't only throw ninja stars exclusively. You gotta be good at other styles of fighting, ultimately you want apply of every style there is.
So, the point is that, having versatility when you playing or practicing it can add a different style to your approach as how to play bass in a more creative way. That's right, switching from a Rickenbacker 4003 to a Fender Precision will give you a different prospective about the instrument itself and of course different feel, sound, plays different.
Having more than bass is OK, as long as they have been played. Let's not forget, an instrument meant to be played, overall.
Ultimately, it is up to personal taste and wallet. If you don't have to sell then, please don't. Keep it, keep'm all...and play!!
I own 4 basses, which may be 3 too many. I never get any real serious practice time in, I always try to decide which bass I like best. I usually bounce back and forth between my Mustang and MusicMaster, only occasionally play my Precision.
3 days ago I would have sworn that I would keep the Mustang forever and ever; but I got a bit tired of the muddy, muffled sound of the open E. So I picked up the MusicMaster, and I'm loving it as much as I ever did.
I often think that any of my basses will sound the same to the average Joe in the audience, and I should sell all but one, only I know I'll regret it later. I guess what it comes down to is my minimalist nature has a desire for my one and only bass. Can anyone relate?