How can i STOP Android from cleaning cache?

recently I've been using Google photos to back up my library of more than 20,000 photos and soon after I finished uploading I discovered I have a problem with the Google photos app.
Every time I open the app it starts pulling thumbnails and adding them to the app cache and when I go through all my albums all thumbnails are loaded and the app caches is at almost 500mb.
The problem is that after a few hours the system automatically cleans cache and then I have to re download the 500mb in order to know my library.
I just want an app or a plugin or even an xposed module any tool or way to stop the system from deleting the thumbnails and forcing me to re download them every time which is very costly in my case

Which phone do you have? I don't think Android is clearing your cache. Maybe your phone came with a special feature or with a cleaner app preinstalled. Search in your settings and in your app drawer for such an option/app and disable it.

I'm running cm 12.1 on nexus 5