Don't even try to do Vikings War of Clans in offerwall.

I'm an idiot to try it. It give 14 days to reach level 32 to maximize the rewards. However, the time used to upgrade important buildings over level 10 is weeks or above (my current upgrade from level 25 to 26 need 100 weeks even spent over several dollars to buy boosts and premium items). This madness is implausible, it just a trick to indirectly take your cash so if you don't feel like to spend several thousand dollars just for some free crowns, I suggest you buy it directly instead of wasting your time and cash there.