I know you can 'restore' it, but it doesn't seem to do anything. It goes down in percent, but no idea what its purpose is.

will it be endless run? Or just replay-again?

It's pretty good, reminds me of Lazerhawk and similar

The "Upgrade any mercenary 2 times" quest seems bugged. I've had it for a few levels; upgraded my main character at least twice, it's still 0/2. Upgraded a new character twice and still 0/2. Other quests like the 'get 1400 money' one worked fine even in the character window; I sold a few weapons worth more then 1400 and it procced immediately, no need to go through a mission....

I am pretty far, but it looks like it wont save given the warning. Is this really have to be beat in 1 sitting?