So I've rather foolishly decided to enter a 60 mile charity bike ride (http://www.sueryder.org/Get-involved/Events/All-events/2013/May/Ride-for-Ryder-Nettlebed). I thought some training would be a good idea. It's all on-road and is due to take place on 12th May. I'll be doing it on my MTB with some slick, or as close as possible, tyres.
Currently I ride to work 2-3 times a week which entails a 10 mile ride each way along a canal tow path and old railway line, plus a bit of road either end. Looking on-line (http://www.doitforcharity.com/cycling-training-guide.aspx) seems to suggest some moderate rides in the week and a longer ride at the weekend. Ramping it up over 10 weeks until you hit the 60-70 mile mark.
My main concern is whether 2x10 mile rides in a week day will be as effective as a 1x20 mile ride. My gut says it won't as my endurance is the main thing I'll be looking to increase.
Any training and other general advice greatly welcomed.