I have the 37" KM2s.
I'm not sure of how long I take but am guessing about 15 minutes for all four. I go from 10 to 35 psi. The per tire is not really long enough to go off and pee (without going over 35 psi) but long enough to get cold doing all four.

 

tested my $60 harbor freight compressor.

37x13.50x16 pro comp xtreme a/t tri-ply sidewall

dropped to 10 psi all 4 tires and full size spare
refill from 10psi to 30 psi: 3 min 17 sec (1 tire)
at 12 min 36 sec on 4th tire compressor shut down on thermal shut off at 22psi
waited 3 minutes to cool down
15 min 36 sec started again from 22 psi to 30 psi 16 min 45 sec
continued to spare
total time 5 tires 20 min 10 sec

i would say thats pretty decent. yes it shut down just under filling the 4th tire, but it still got the job done fairly quickly just under 17 minutes and even filling the spare in about 20 minutes

atleast for now, i will stick with what i have, it does the job, so what if i have to wait a few more minutes, if my jeepin buddies can;t wait 5 minutes when camp is packed up and ready to leave, then the hell with them and i will catch up a mile down the road.