I have a S2S sleeping bag liner for use with my ZPacks 30 degree bag. I have it for two reasons. First to add warmth, maybe 5 degrees? And second, to keep my bag a little cleaner so that I don't have to wash it on my thru hike (or as often). It weighs 8.5 oz. So the question is should I skip the liner and just add a 4 oz pair of long underwear? The long underwear coupled with a light top layer would probably be warmer than the liner. I could also wear them on those days when its a little too cold for shorts but to warm for my convertible pants. If the above is true, then is the idea of keeping the inside of my bag cleaner really an issue? I am leaving on my thru hike on April 5th so it shouldn't be cold at night for very long. What do you think?