On my first playthrough, I found I died a lot, even on the later years. On my second, I got the Giant Coffee Mug charm pretty early (+200 energy, but damage is increased by 1). I found this item made a bit of a snowball effect, especially on the levels with fewer kids. There were times when I approached 400 energy. And with the 40% energy carryover (this was before the difficulty tweak), those larger numbers really make a difference for the next year.
I played through the entire game that second time without a single loss of life. I think the worst I did was one year when I dropped below 100 energy. I was never at a loss for charms, berries, bunnies, coins (at one point having 40+ of those) etc.