if you're using Griffins you may find Timeback very useful:
-at the beginning of your turn send them forward and wait for attacks of all enemy melee units (Griffins retaliate every time! you can cast Magic Spring on them for some mana filling). Next turn same thing and at the end of this turn cast Timeback on Griffins^^ two turns for free
-this is kinda risky but: split your griffins and send them into fight. At the end of next turn cast Timeback on original stack. They'll become unleadershiped and out of your control but as I observed still attacking enemy units (like under Berserk spell). I'm playing on Normal and maybe on Hard and Impossible they'll start attacking your own troops, I don't know. Works fine on Normal and you don't need to bother with any loses of them.
I use Timeback also on Cannoneers for second Salvo, on Inqs for Ressurection for my Dragons, on Royal Snakes after some wild fight under Berserk spell, on tanking unit under Target spell if taken massive loses and many other times you will figure out yourself during battle
but remeber to not occupy previous position of the unit you want to Timeback with your own troop (and try to foresee computer moves)