Hi, yes I am sure that for each loop will be very time consuming plus you would have to know the number of items inside of your sheet to carry on with loop, the more the number of items and attributes are there in the sheet the more time consuming it becomes.
In my opinion use read range activity, it is much more efficient for doing the same task. It can read your entire file at once or even a particular number of entries based on your requirements.
hope this helps cheers !!!