This is obviously a mobile only issue. Also I appreciate that this is a free game and ads help keep games alive. Want to caveat with the fact I tried to pay for the no ads version but I have an issue with my google account so that's a me problem.
The 5second shippable ads are obviously ideal. 15s are also definitely fine. 30s ones suck but I can deal with the odd one as they don't seem too common. However I've recently been receiving 60s ads, and just had 4 in a row! (Daily cps, double coins and souls, silver boxes, minions cooldown). I think 60s is too much, so would respectfully ask if those could be removed.