I usually don't mash, but don't drop down much in the granny gears either - I've slowly built up a tolerance (I guess) and have only been using the top 4 cogs of the 21 speeds I have.

Sometimes I'll mash, and I do it because I know I have the energy, and I know if I really give 'er in a fairly tall gear, it'll get me up the hill faster - and sometimes I just love the extra hard work of mashing. I don't mash when I've got the trailer on the back though, I'll drop down and spin - I just feel safer and I'd probably do myself some injury mashing with ~60lbs towing behind me

It's rare I'll drop down to the middle ring on the front, so far rarer to use the granny cog - only when I really really need to do I touch them - and that's usually in the MUPs, coming out of the valley in some spots isn't paved, and needs some decent effort at times.