That's usually the best method to make sure it's right. Outside during the winter, 2 hours should be enough (assuming below freezing) though. If allowed to get low, air bubbles do become a nuisance though, and either the incline filling method or driving for a day or two are what's needed to get the last little air pockets out. Or a combo of both.

OP, I feel your pain. I found out 1 week after buying mine hat the tank was leaking. Stealer of course didn't want to fix. $500. :P Will do the thermostat and hoses in the spring, though conventional wisdom says do it all when the tank fails.

Well mine just broke - my son was going to judge a debate meet on Sat. and told me "the check coolant light is on". After he was done I told him to pour some water in the radiator and sure enough, it all ran out. Had it flatbeded to the BMW dealer where he was in South Bend and $596 later, I have a new expansion tank and some sort of trans thermostat that they said usually breaks and needs replacing. No skin off their nose, but another $124 our of my pocket.
I think I might pull a switch and have him drive my 2007 Pontiac Torrent, while I keep the X5 here. I can't fix it if it isn't in my gagage, and the Torrent is scads more reliable than the X.
Bill