many anemones do deflate on a regular basis. COMPLETELY deflate as a way to expel water and the wastes in it, and reflate with clean water " a fresh start" Many anemones do this on a daily basis.
Do you feed your LTA every day? If he doesnt have to wait a few days for food here and there, he will not open as much as he doesnt need to 'catch' anything. Anemones get used to eating and get 'spoiled' kind of.
Can you post more information about your tank like temp, lighting, nitrates, etc.
What are you feeding and how often.
What size tank is he in?