Hi… This part isn’t really documented, but, no, the Machine isn’t accumulating burst balance while stopped. (That would effectively be free CPU time, once it did wake back up.) The previous balance instead just carries over unchanged across normal restarts, with an unfortunate exception for redeploys:
https://community.fly.io/t/predictable-processor-performance/22259/110
(A redeploy counts as a separate “version” in this context, as I understand it.)