The batteries in my 09 started to die last season... Pain in the ass with the warning popping up and blocking the display all the time. The dealer wouldn't replace them under warranty until they came on steadily, which they did this spring. Last spring my OEM warranty was ending, but I took the advice of everyone on the Connie board and bought the extended warranty online for $300 something. The TPMS batteries are covered under it. Back in May I took it in, showed them the "battery low" lights were on, and they replaced both for free under the extended Kawi warranty. Without the warranty it would have cost more than the cost of warranty! I also bought a new front PR4 for $10 more than the cheapest one I could find online and they installed it for me for $20, mounted and balanced.
Some folks have had ok experiences with taking apart their original TPMS sensors and soldering in new batteries, however newer models and replacement Kawi TPMS sensors have been changed, and I think this is tougher now. Check out the Connie boards, there may even be someone on there running a kitchen table service for putting in new batteries.
Another note on the extended warranty...as the original owner I can renew it at least one more time.... so for around $700 or so I'll have a bumper to bumper warranty on the bike for 9 years! Can't beat that with a stick.