Best practices for calling finish() on an activity in android?

While you may reload all your data on returning to the activity, there is still no point on calling finish().

When activities are hidden, they do not use resources, and are of no real problem. Just leave them as is, and then when the user navigates back, it will reload it as required.

In this state, they can also be garbage collected if required - which is all taken care of by android.