they will start to lose shape, more slowly the later you remove it, but will still start to occur. maybe some really old stiff, woody branch won't bend much, but most will start to reach up again.
a coulpe of my ggxww diaries have a LST'd plant that i removed or allowed the plant to simply break free of, i can't recall. i purposefully used staples in side of fabric bag so that any force would remove the staple before damaging the plant.