That's my only concern about playing 5 string exclusively. A couple times I've sat in with bands and had to play four string; it's a challenge.
On the other hand, I once had fun when someone sat in with my band, not realizing I was playing a five string. I laughed with him, not at him. He was as uncomfortable on fiver as I was on four. I've felt your pain, buddy!
Hey, I only play 5 or 6 these days, but I can handle it if handed a 4, 5, 6, 7, 8, 10, 12, 15 string bass even if fretless! Because I played 4 for years and and 8 or 12 is just like a 4 and now I play 5 and 6 (basically the same instrument as a 5 where the 6 has greater range) and a 10 is like a 5 and a 7 is like a 6 with greater range (though I'm a 7 string noob and don't quite know what to do with that extra range)
However, I can say that in my opinion life would have been better had I been playing 5ers and 6ers right from the start and would freak if handed a 4! Worst jam session ever was when no bass was available and I was handed a guitar to play bass on the 4 lowest strings! Yeah, I did it because I play guitar too.
