Lvl 1 = 2 days
lvl 2 = 4 days
lvl 3 = 6 days
lvl 4 = 8 days
lvl 5 = 10 days
lvl 6 = 12 days
as you can see the upgrade time increases by 2 days every time. So it's fair to say:
Lvl 7 = 14 days now
Now If you add all these days up it'll sum up to a total of 56 days. So maxing 1 Tesla takes 56 DAYS. That's almost 2 months. Supercell please do something about this.

