Have you tried hand washing a down bag? I have. It took me a lot of time, effort and a full bathtub to get them soaked. If you're keeping your bag wrapped while riding and sleeping in a tent, how are you going to find all that water to soak your bag?

As far as a synthetic sleeping bag staying warm, that's a myth or misstatement. It also loses warmth. Try it for yourself. Heck, try it tonight. I bet your nights are already cold enough to provide a good

While a synthetic bag may be cheaper initially, they don't last as long as down bags and accordingly have very depressed resale value.

From what I've seen, the people that have problems with down sleeping bags are the new and reckless. The folks that don't adequately protect their sleeping bag while travelling, sleep directly on the ground, and pitch their tent very poorly and then allowing their sleeping bag to touch the tent wall...along with other mistakes. Even then, it results in a cold night, but I've never seen a total loss of insulation. Those mistakes can be prevented with education before heading out on a trip. The small amount of moisture that collects can easily be eliminated with a brief stop at a laundromat or a longer stop to lay the bag out in the sun.

There are two occasions when I think there's good reason for a synthetic bag. The first is when nights hover in the high 30°F's with very high humidity (pea soup fog). The second is during an extended outing in sub-freezing conditions when there won't be an opportunity to dry out gear, and preferably weight is not carried. These two result in sweat vapor condescending in the insulation, and in the second it'll accumulate throughout the trip.