I love my WM highlite (35f sewn through baffles) for the 3 seasson. Most of my 3 season is down in higher eleveations where 40f at night is considered the norm if not a tad below. Last weekend I slept in it down to 25f but it was in my Tigoat (old one witht he purple bottom) and I also had on silk weight capiline top and bottom all under my tarp. So for me I recommend a 30-40f range bag for the 3 season. Prefurably a good 800+down fill bag, but id the budget is tight then a super light syn bag will work as well. If I know it is not going to get below 60 at night I drop the bag and just take my bivy and sleep in it with my cloths on.