It wasn't a speedwork session - it was an exception to my norm of training outside. What I meant was that I typically use the turbo for speedwork and only every now and then will I do a long ride on it.
"turbo where I do high cadence sub 30 sec spins and 3 - 5 min max efforts" I'd do less of this and aim for longer efforts. I only do short stuff if I'm having a crack at a late season 10 or something.
How much longer than 4hrs are your long rides? MSRs a long way..
Also, thanks for the tip.