For the time since then I can say it’s a bit inconsistent for me, but it certainly behaves good enough to not go back to stock for this.
Until now, /e/ for me never quite got to the battery life I got out of the stock OS, but usually it gets close to that.
You can see I got about 0.33% battery decrease per hour when idle with the stock OS (although not in stock condition), now I usually get about 0.5% battery decrease per hour when idle with /e/.
Occasionally this goes up to 1% or even 2% per hour when idle for me, but only for a while, and then it’s back to normal again without me doing anything. I haven’t figured out what the cause is, yet. I could imagine e.g. the Mail App occasionally taking longer to sync my mail accounts, but I’m not going to watch the phone for hours to wait whether I can catch it in the act 
.
As long as it gets back to normal by itself, I consider that good enough for me.
I installed /e/ on my backup Fairphone 2, too, and battery life is the same as with LineageOS 16.0 for microG before.