I like Smartwool merino wool base layers year round. Used a short sleeve and long sleeve version this summer, including on a week long backcountry trip. For that trip I also wore Icebreaker wool boxers instead of padded shorts. As temps drop I'll add wool socks and a wool hat under the helmet. When it drops to near or below freezing I'll add a wool mid layer. Below zero F I switch from a thin synthetic balaclava to a wool one.

On my week long trip I was soaked for three straight days. The wool boxers kept me from getting any saddle sores. Not sure padded shorts would have done the same.