That's pretty excessive. How often are you gigging?
Wireless and an active bass are two very different things when it comes to batteries.
Was thinking the same thing - I typically gig 8-10 times per month, and still change my batteries every 6 months - never had one die on me yet... I also use rechargeables for my wireless needs - it makes alot of sense, since wireless eats up batteries pretty fast...
- georgestrings