How often do you show interstitials?

Soon I’ll be launching my first game and I’m setting up the ads right now. It’s a game with lots of levels which on average maybe takes 30-45 seconds to complete. My question is about how often I can show interstitials without upsetting the user to much. I was thinking about showing it every time the user completes 10 levels… What do you think about that? To often?

How often do you show them?

Following is best you can do:
one at launch
one at completion of every 10 levels (or 5 if passing each level takes time)
one at exit

couple the above with a remove ads in-app purchase.

In my tamagotchi - like game I show it when user exits minigame or on game exit, also the ads are shown no more than 1 for every 5 minutes. It makes users never complain about ads, I have ecpm with admob 1-1.5$, but I don’t think that it is earnings-optimal solution.
In smaller utility apps I show intersitial only on exit. Results are similiar.

Thanks for the advice! Sounds good to combine level completion with a time factor. It’s really annoying when apps shows to many ads.