I've been doing it this year in a bid to get fit. I don't have the time to spend nearly 2 hours a day training otherwise.
My route is 28.9km each way, which is what, 18 miles? It's anything between 45-55 minutes each way, depending on energy levels & motivation to bury myself.
I find 2 days in a row really is my limit to be able to function normally & by the time I get home on the second day i'm pretty wrecked. I try and stick to 3 times a week, and I would say i've hovered between 2 & 3 times since March.
It's made a huge difference to my fitness, and i've had to eat like a horse to stop myself from turning into a rake. It can be a pain in the arse, as I play squash to a decent level also, and trying to fit everything around that and county league matches is difficult at times, plus I want to ride XC & DH at the weekend too.
I don't think I could do 5 days a week and still ride at weekends, sometimes the motivation drops, and i'll sack it off for a week, but I find now i'm much fitter, i've got an abundance of energy so have to get out on the bike. I'm planning on stopping soon when the clocks change as gearing up for winter is going to be too cost prohibitive on a reasonably exposed route, so will break out the turbo and try to build on a half decent base I now have.
The key I find to keeping me sane is some sort of structure. I couldn't do it on autopilot every day on the same route, and I can't really vary my journey without adding serious distance on, so depending on feelings i'll do random intervals, chase down people/cars/mopeds, force minimum speeds on climbs, HR minimum goals etc. Normally i'll do that one way and have a cruise on the other. I find it seems to work well.
Until you try it, it's hard to know what your limit is. About 20 miles and an hour max is my limit. For you, it maybe more.
