I have a really good tip that I use. If you want to freeze an enemy for a A LOT longer, use an attack that causes 'freeze'. I use the spear of Poseidon, so I attack big enemies (Cyclops, Centaur guards, Juggernauts) with L1+ and that makes them 'freeze'/go slow motion If you hit them with Crest magic while they're like this, they stay frozen for absolutely ages. I have never seen an enemy break out of the ice like this, you can keep attacking them until they break. It is EXTREMELY Useful.
It works on every enemy except for Hercules, the Chimera, the Manticore and the Olympian Sentinal. When I say it doesn't work, I mean you can't freeze and shatter them, but you can still sort of freeze them. Hope this helps