I've been thinking for a while that I might like to run in a marathon or walk in the *** cancer 3-day.  I've participated in 5k and 10k's before, but I've never kept on going for miles and miles and miles like I would need to for something like that.

Does anyone have any idea how long it might take to train for something like that?  Anyone know how to train for that?

 well, I have never done anything like that, but i guess that you need to train for endurance, so, lots of running for very long distances, and lots of eating the right things - If i were your I would go to the local running track and ask about - I'm sure someone there would know what you need to do, or at least would be ble to point you in the right direction =)

 I think that you can prepair for any competition like this by duplicating the scenerio and practicing it over and over.  If you have to run 10 miles, practice a ten mile run.  The main thing is building your endurance up until you can achieve the lenth, then you will have to continue and work on your time.  This will not be an overnight practice session, this will take months to prepair for.

I usually participate in one "Walk for ?" activity every year but since it's just walking, I never really do any training for it.  For a marathon, I should think you would definitely want to to some long term training.  Obviously, running would be a huge part of your training but I should think some strength and endurance training would also be beneficial.

 good point - I dont think I could run a marathon, but Ido think that if i trained enought (6 months, or a year) then I could run one - its all about getting used to the distance- If you train every day doing a 10k run and on the last day of the week do a practice marathon then I'm sure that If you repeated it enough it would get easy ! 

Lots of us here in the UK do small runs for charity like the "Run for Life" for *** cancer. There are a lot of local charities that sponsor these and the runs are anything from a mile around the local park to several miles from one village to another. I could only walk around the park the first time I did it but I now run 10 miles at a time. If I keep it up I think I could do the London Marathon. Its a case of building a little bit more each time.

 Thanks for all the great suggestions!  The 3-day walk for the cure thing is 20 miles a day, I think.  I know it's just walking, but it seems a lot more daunting than running a marathon and just getting it all over and done with in one fell swoop.

I'll definitely check out  what other have to say at the track.  I don't know why I didn't think of that.