wow, what amps you at,
I use an 11 for as much as possible, high amp mig/mag as high as possible 12-13, ploughing in multi pass runs, you dont need to see as much detail,
TIG again 11 unless low amp work and then its down to a 10, possibly a 9,
My thoughts are, you only get one pair of eyes, look after them and give them a chance.
I start at shade 9 which would be up to about 50 amps DC and max my helmet out at shade 13 by about 160amps DC. I have done short runs at 200 amps AC and think I would have gone to shade 14 if I had it.
Making sure the work is well lit and there are no bright lights behind me helps visability more than going down a shade or 2.