How much playtime to clear stage 50 in a week?

I've been playing about 4 hours a day for 5 days, doing various things, but clearing stage 50 seems nearly impossible. Surprisingly, I can only get past 40 stages by skipping a lot of ads. Weapon upgrades also require watching ads to increase experience. On average, it takes about 10 stages per level, and I need to watch around 500 ads to clear 50 stages.