User sees too many ads. Ads stop working

So, I released a new game, and we made a design totally ad centered. The play sessions are very small (1 to 10 minutes), and then an Ad Button appear, so they can obtain a reward.

From what I heard from my users, they LOVE clicking the ad button to get their reward, this means that our design is a success, but here`s the problem - many users are complaining that, if they watch too many ads - one at the end of a play session, they soon stop working. From my observations, the ads stop working between 15-30 visualizations, and they start working again whenever they want, tipically when you don`t touch the game for some hours (8-10 hours)

Does anybody know why is this happening? Thanks

 

The Monetization FAQ state that each user is limited to 25 ads per day:

Q: Why am I only seeing 2 or 3 ads at a time?

That's probably it.

 

adding to the above reply (a little irrelevant to the question)... in my experience, if users see ads more frequent that 5 mins, the eCPM drops and the additional ads do not generate any revenue...