Honestly those kind of apps are power hugs and pretty much run in the background the whole time plus if you have it just to clear cache you might want to download an app that just clears your cache or restart your phone. Clearing your RAM makes no use as the apps that need to be running in the background will just open back up and it could even slow down your phone. I personally used clean master for a few months when I had my Note 3 after reading online how useless that app was I haven't used it again and haven't noticed my phone acting any different performance wise meaning speed boost. Pretty much the app is just another BS app to be honest with you my phone had more lag with the app installed. Antivirus apps might be necessary if you are the kind of user that likes to side load things on to your phone but again as those kind of apps run constantly in the background it could slow down your phone performance wise and even lower battery life.