I have the same problem. It seems than when I start/restart computer that 15 minutes inactivity timer is working correctly but then after couple of days computer usage (with many times putting computer to sleep) mouse starts to sleep after one minute inactivity. Off course shorter sleep duration saves battery, but this mouse has so slow wakeup (compared to competitors mouses) that it sometimes drives me crazy (e.g. writing something for minute or two, then I have to do something with mouse, but mouse sleeps already so I have to either move mouse rapidly all over the mousepad or push button and wait that second or two so it will wakeup and starts to work)
This problem appeared after updating to latest v3.35 firmware.
Also with this newest firmware it seems that when I put computer to sleep then sometimes mouse doesn't go to sleep. Instead mouse goes to HW profile and starts changing colors. This won't happen every time, I would say it only happens once in 5 to 10 sleeps. I think that I didn't have this problem with that older firmware.