Thermolite vs Merino

For the merino and lycra and stuff, I just use a very mild non-bio. I now only own 1 HH-esque poly-propelene top which I have to hot wash with nasty detergent to get clean, and even then it's a bit smelly.

Base-layers for more than 2 days... never been touring, or camping?! 5 days in my merino top on a climbing trip was the longest between washes - despite lots of physical exertion and sleeping in it, it was still passable* at the end. Long lasting thermals are a real bonus, because you only have to buy a couple to see you good.

(*at least relative to the rest of me!)

Thats the problem right there, you are using crap washing liquid to wash a very dirty base-layer, you need to use decent stuff, which will also improve the life of your base-layer, and negate the need for you to do stupid things like put it on a hot-wash with nasty detergent, which will damage the wicking properties of it and you might as well throw it in the bin after!

Wash as per the label with this stuff: http://www.gooutdoors.co.uk/womens-clothing/cleaning-and-treating/nikwax-base-wash-300ml/COREAWBE141