been using easytether on my old android for 2 years and never been charged. the wifes new android creates an access point which is built in and we use this when the house internet goes down. theres a pc, 2 laptops and 2 sat boxes (not sky) that used that all day for 10 days. granted nobody watched iplayer or downloaded films.
never needed to root any phones yet to get them to do what we need