In my app, I plan to have around 3000 CKRecords which I will retrieve and place all of them in an array. I will later have to loop through that array several times. Is this a good time to use NSMutuableArray?
Sure, but CKRecords are key-value pairs which are themselves mutable. So I would think you could still get away with NSArray if you want to move CKRecords. The array doesnt have to be mutable, just the records themselves.
When the data is varying then we must use Mutable array or else if it is not changing just use an array . a Simple logic to remember .