Then I'd say 36 hours without sleep if the adderal is just wearing off and you're popping the vyvanse. Lisdexamphetamine tends to last 12-16 hours with a strung out come down ime.
You won't die but you may wish you were dead is my point. Not to mention amp abuse is difficult on the heart, Amp comedowns and being strung out is not fun in the slightest.
If I were you I'd skip the vyvanse and find some downer like booze to take the edge off and get towards sleeping.