IME, vyvanse is hard to do too much of. I wouldn't redoes, simply because for your sake, insomnia will further neurotoxicity, and you will basically feel like shit for a few days, whereas If you take just the one dose, you won't crash, you'll sleep fine, and your brain will leave without a scratch (well, not a noticeable scratch, at least, there is still some damage, but it will heal.
Are you using for recreation or for add, cause vyvanse IMO has little rec value, and isn't great for add either. It just gives me a slightly pleasant sensation throughout most of the day and a dry mouth that can't be cured. I notice that a few people I know as well as a few bluelighters consider it their ex stim of choice. This is odd, because vyvanse is designed to be a less recreational and jittery stim, and is the preffered add med for patients with a history of drug abuse, particularly stimulant abuse. It's d-amp, but it's nothing like d-amp. D-amp is the closest relative to meth, whereas vyvanse makes an excellent substitute for caffeine, as it lasts longer and has less of a crash.
All that being said, if you must redose, be prepared with antioxidants (weed is the best, as it stimulates appetite as well as promoting relaxation), l-tyrosine (if you can't find the pills, it is found in meat, which type of meat I can't remember, but look it up), CHELATED MAGNESIUM (thought I'd say that before tricomb comes and says it), and personally, valerian root and kava kava together work great for anxiety and body tension. Some more things would be B vitamins, vitamin c, and D (creates melatonin. If you have Xanax, then you don't need about half of those things, cause Xanax alone will make you feel better than all the items I listed above, although the vitamins, tyrosine, weed and magnesium are nessecary if you want to exercise harm reduction and save your brain and body a lot of stress and damage.
EDIT: dammit tricomb, I thought I had you beat on that one!