Depends. I assume you want to put that effect on a custom emblem (because those can't be interacted with), and that you want to add the effect to ensure games end. Adding such an effect will make two strategies stronger: life gain and aggro. Life is a foil to aggro as well, so I think you need to curate your life gain effects if you add this effect. If you want to strengthen aggro decks (beyond your cube's composition), pick a purposefully low number. If you merely want to add the effect so that rounds don't go to time, pick a higher number. I'm pretty sure no one here ever tried this out, so you're going to have to figure the right numbers out for yourself.