Cheers, only just made the step up to 40 mins from 35~. I'd keep going up in time and leave the speed the same but from what I understand the catabolic effects on muscles after ~45mins cardio aren't worth the extra fat shredding.
Program it for stamina training, so it goes up and down. Something like 9.3 for 3 minutes, then rises to 13.2 for 3:30mins, then back down 4 times. Manager to cover 3.75km in 20mins.
start about 12 and build up to the max of 16 (km/h) over the course of 3.2 Km which means i do it in about 14 and a half to 15 minutes. Any longer and I start getting realy bored, even with music!