A colleague's son is off to Mongolia July/Aug this year, heading into mountainous north at first, and Gobi desert later.

Since he's still at school, I don't expect they'll be doing anything too serious.

Does anyone have any kit or other advice I could pass on, or experience of trekking in the area?

The kit list provided looks reasonable, but seems to be lacking a decent warmth layer, such a duvet (synthetic or otherwise).

Cheers.