Hello!

In the beginning sorry for my English. I'm creating movie recommender based on TMDb and I have one problem, because I need to store data, but in license is:

Cache any TMDb metadata or photos other than for reasonable periods in order to provide your service.

But I need to store data for longer time, because I need to have connections between films, persons, genres. I have one other option. I can save just IDs, but it is impractical for me in future.

So I have one question: What is reasonable period?

Thanks for answer.