I was about to balk at "never recuperate" because I didn't see how that jibed with "grow in power over time." But now I want to know if you're speculating about "essence" vs. "mana" or if I've missed some dev chat. The distinction seeems to have *lots* of interesting potential.
Maybe one way your "essence" might grow is through sustained control of a Shard, which also provides "mana" flow for ordinary spell-casting and maintenance. So you still might effectively 'recuperate' from restoring lands or enchanting a hero, just not quickly and not if you lose control of your Shard(s).
Think of it like this. X is your essence. As you level, you'll get X+1 every level. When you spend essence, you're taking X-1.
Now, if you never spent any essence, you'd have X1 in essence, but if you did, you'll be back down to X. Spent essence never gets returned, but you do increase in power - how you choose to spend that power is entirely up to you.
Also, it's to my understanding that mana and essence is seperate things. Mana is something you use to cast spells. Essence is a part of "you", the channeler. Again, this is all just what I've read into the articles and dev comments. I could be completely wrong.
Edit: In a nutshell, 'essence' seem to be what makes you, the channeler, the channeler. By transfering essence and imbuing your heroes, you'll allow them to cast spells, for example. This doesn't make them channelers, because their essence is finite, while yours supposedly grows.
