If you are already capable of running 13 miles (as you clearly are) I don't think you need an 8 month marathon programme, there is a reason why most of them are around 4 months or thereabouts as this is an appropriate length of time to build up to marathon fitness. What I would probably do is just keep your running ticking over in the meantime, maybe enter a few other races (10k's or even another half) and start marathon specific training about 4 months before your planned event.
Good luck with it; which marathon do you have in mind?
Can anyone help? I'm trying to import one of the RW marathon schedules to my Garmin 405 and failing miserably I've managed to import it to Garmin Training Centre, but whenever I try "send to device" I just get "there is a problem communicating with your device, check it is connected and try again". But I know it is connected because I can transfer data to the computer no problem.
There is probably a simple way of doing this but I'm not very good with technology! Any advice would be welcome, thank you.