We usually go out for a couple hours at a time. As it's almost 50/50 uphill and down. He prefers to stand and pump, but I usually fuss at him to sit and spin (conditioning for road racing). We'll probably head out in a few days (supposed to finally get over 40 degrees).
This is one of our favourite places to ride
http://trails.mtbr.com/cat/united-st...0_4578crx.aspx .