Nobody's indispensible.
Not me, not you.
If they have a will to carry on, they will.
I know these guys are your bud's.
So you are going to have emotions about leaving.
No disrespect is intended with these comments but if you leave they'll just have to make do. Or not.
EDIT:
Why is it that the bass player always seems to have the PA?
Same in my band, same as the last band and same with my buddies band.