The Logitech Marathon M705 is known for having a super long battery life as well as other useful features:
- 2.4 GHz connection strength
- 3 year battery life
- Laser tracking
- Unifying receiver for up to 6 compatible wireless devices
- Programmable buttons
The Wirecutter even did a study of 90 hours of research on ~200 mice, surveying 1,000+ mouse users, testing 25 mice ourselves, and consulting a test panel of experts and laypeople and concluded that this mice is the best in the market.
Buy it on Amazon for ~$34: http://www.amazon.com/dp/B003TG75EG/ref=cm_sw_su_dp