This is nuts, and a fantastic achievement, both. I have a state of the art push longboard (Dregs Uptown, probably the lowest deck you can buy except for a landYacht, 72mm wheels, very clean Red bearings) and I've injured my achilles a few times on 8-10 mile skate outings.
I was tempted to use a longboard but it just didn't sit well with me. So I managed to do it on my shortboard and am so happy I went with that decision, although my ankles would say otherwise
Although you wrote you'll never do it again, IF you were to do it again anyway some day I would like to advice you to have another look into a longboard, and choose a day when it's nice weather! You'll have a lot of more fun riding.
Check out http://pavedwave.org/ (The Soul of Distance Skateboarding). On the forums you'll find tons of advice (skateboard equipment, technique, nutrition) which can help you achieve awesome goals. You can also find events over there. If there's one time an event close to you you should really check it out, it's a great experience to come together and ride for 24 hours! (sound funny huh)
http://www.silverfishlongboarding.com/forum/general-longboar...
also, i did the drive from Sydney to Brisbane with a couple surfboards, highly recommended. Next time i'll do S to W (in a campervan)