Time between showing next video?

Vungle
#1

I wonder how much time should be between showing an ad and then the next one?

I want to use the video ads for giving players some ingame value by watching the ads. Theoretically players can watch ad after ad but I would like to know if this makes sense, or if there should be a delay until a next ad could be watched?

#2

I wonder because I have noticed I have watched about 50 testvideos so far with about 30 to 40 finished 100% and in the vungle testinfo for the app I get only 8 watched videos and 2 finished.

So what is the best practice to implement it to get the info for all watched video ads?

#3

I wonder because I have noticed I have watched about 50 testvideos so far with about 30 to 40 finished 100% and in the vungle testinfo for the app I get only 8 watched videos and 2 finished.

So what is the best practice to implement it to get the info for all watched video ads?