I know the difference between TrueSync and Sync for Desktop is that former doesn't store files locally but indexes them, shows them on Z drive & only access them when needed. (If I have frequently used folder, I should probably use Desktop Sync leveraging it's selective folder sync option). 

But you can notice option to select "Cache Drive" (on Windows C or D etc.) where cache files are stored for WorkDriveTS app.

My question is : how long files stays in local device while using TrueSync? Is there condition, logic it follows with the default setting of 'online only' selected? (Just a general question, not an urgent query)

Recently I uploaded/copied a large media file on WorkDrive folder. Couple of days later I wanted to work on that file, when tried to access the file from the same PC where it was store, it got downloaded from WorkDrive cloud. (Made me wait for 10 mins for download).  In this case, I should have marked it as "available offline" than the default value "online only". 

Therefore my concern is, when there's no storage crunch at local PC and selected cache drive has plenty of free space, should files follow rule of inertia and be there on device unless provoked to move to cloud due to storage shortage?