+1 for wool
+1 for wool of appropriate thickness/layers. For my mileage Icebreaker > Smartwool especially on wear/longevity. Equally as soft. Pricey up front but good value over their life. Ibex is another long wearing line but I find it slightly less comfortable.
Hot/warm temps = liner weights. Double them up with a second light weight or add a heavier weight or simply replace them with a heavier weight to cover a wide range of temps.
I like over-the-calf length (or "ski" length) regardless of the boot height I wear (but mostly my boots = vendramini marathons).
All my first layers - sox, shorts & shirt - are Icebreaker (ultra-fine merino) wool when on IBA rides, camping rides, etc. Next layer up I often switch to synthetics. This combo prevents stink, is great wicking and offers great body temp regulation, warm or cold weather.
I do recommend cleaning wool clothing with wool-specific detergents: Nikwax, McNett, etc. Which you can tote along in small amounts for occasional hand washing in a basin.
Enjoy your trip,
'02 ST4s (r.i.p.)