So today i noticed i still have the VIP 60 min elixir combo and dont see a better way to use it than farming locked at km3 while getting exp.
The elixir provides 60% exp gain and 30%(+15 from jack= 45%) luck. My question is:

IF i use another exp elixir will i just waste it or the exp will get to (60+25=)85?
I think luck doesnt stack if i can remember but does Xp?