I drop it into the lowest of my low (26 front 34 rear) on my loaded touring bike up most every long climb.
it's nice to keep it in 2nd though, and keep extreme low as a resting gear even during fierce, multi hour climbs....drop into crawling granny, grab some drinks and snacks on the fly, relax for a couple of minutes, then pop back up into 2nd to continue the grind.