Is there a reason why summit stores such amount of data and can it be controlled within the app?

I use Summit daily and Summit typically uses 300 - 500MB on disk so 1.5GB does seem abnormally large to me. It's generally expected that most of the cached data is of videos and images as those are the largest types of data. If you watch a lot of videos using the app that might explain the size.

Will the data stored by summit keep creeping up or does it reach a certain level and stop from increasing?

Most of the data caches used by Summit have maximum limits on them. The only cache without a limit is the offline mode cache. Typically the largest cache however is the media cache which caches images and videos. The size of this cache is 2% of device's free space, however it maxes out at 250MB.

Summit should be managing your cache so you shouldn't need to clear it manually. You can check Settings -> Cache for an overview of what type of data is in the cache. You can also look at the app's storage usage in the app info screen in Android Settings.

If it still doesn't look right can you please let me know what how much data is used for Cache and how much is used for Data? You can find these values in Android Settings > Apps > Summit > Storage.

The in-app cache overview graph is a bit outdated. I will update the graph in the next release so it shows more details.