I4U NEWS reviews the Saitek Obsidian Wireless Mouse.
In the hand the Saitek Obsidian is wider and lower profile than typical mice such as those from Logitech. Battery life is very good with one battery lasting my entire work day, and I use the mouse very heavily.Saitek Obsidian Wireless Mouse Review
I would peg battery life at about 6 hours which is right on par with the Logitech G7 that I normally use.