I have the Rab's due to QG's recommendation. They last me about a year until they develop holes in the fingertips (your nails may vary), so about as long as pure merino liners.
QG, cheers for the prompt on Devold - I recently realised that my merino base layers are 8+ years old (hence the holes in the elbows) and ibex what I used to buy from have started cutting their wool with poly.