Man it depends on what I am doing. If I am dragging a sled the time and speed depends on the load. As do all the movments, and excersizes.
Generally for GPP sessions I just do what feels right. I don't do a rep set scheme. I go toss a keg or swing a hammer. Sometimes for time. Sometimes till I'm wiped the hell out.
GPP= getting prepared that means lifting heavy things, doing long drawn out tasks of lesser resistance, and everything in between. Mix it up and keep it fun.
Just my 2 cc