For several years I have done 12 on 6 off and count the 6 off as deco time
- it is inline with the recent training that I have had. When times do not fit into multiples of 6 it is possible to alter the ratio slightly but this becomes less and less important as the length of stop increase. For example for 20 min I might do 12 on 3 off switch back and then ascend slowly. As with all things I suggest you don't learn off the internet and certainly never ever trust anything I or especially STN quote
Graham