With the x2, go with rechargeable 9v batteries for practice and rehearsal (in the transmitter). Save the alkalines for gigs. Only minus for rechargeable is that their life is not always predictable.
I picked up a pair of the iPower 9v rechargeables. I get up to around 7 hours total time per battery. That's as good as an alkaline or better. Having 2 of them, I always have one fully charged as backup.
MX