My rule is to never wear outer clothing in my sleeping bag. I have a quick drying base layer that I wash every day after hiking and wear that and my summer weight long johns in the bag. I also wash myself (jump in the lake or a bucket bath) at the end of every hiking day. Do it immediately after you stop hiking, when you are already over-heated, and it will not be that bad. Just rinsing off the sweat and dust helps. I have washed my bag once in 10 years. It really did well- even had more loft after I washed it. I think OM posted some really good instructions on how to wash a down bag. I followed her suggestions and it really worked!