Hi Nexus_77,
We get about 2 - 3 months before needing a recharge of the internal battery for the Vision KeyFob via USB. Only takes an hour or so to fully change.
I strongly recommend one of these over the Aeotec Keyfobs - both versions (four and single buttons). I have tried both versions and I'm not impressed...
FYI - More Info on the Vision KeyFob: http://www.visionsecurity.com.tw/index.php?option=product&lang=en&task=pageinfo&id=30&belongid=148&index=0
I hope this helps.