How is the always on display battery life compared to Venu 2/2 Plus?

Based on 2 weeks experience only ... 

I use AOD, with Pulse Ox during sleep, high sensitivity on gesture, short timeout and low luminosity (those parameters are important, too). Even with AOD activated, most watch faces will enter a low power mode when not looking at the watch, which reduces the drained power. But not all faces are equally efficient, so definitely another factor to consider. If finally you add the fact that timed activities also consume more battery, it's not just "AOD ON/OFF" in the end ... Hence the "up to 5 days".

That said, and to finally answer your question: I'm very close to 5 days using AOD but never achieve it yet. Not because of the watch, but because I never had the opportunity to let the battery level go under 10-15%. In short, I feel - so far - confident leaving for a 4 days trip without a charger, where the Venu 2 plus would have died beginning of the third day (same settings, same face, same usage).With limited timed activities, 5 days are very plausible.

I just posted this in a different thread, but copied it here for your convenience.

My Venu 3 uses about 20% per day. This is with AOD on, auto-brightness, about 40 minutes of GPS every day, two additional activities about three days a week, and sleep tracking every night. With these same settings, my Venu 2 Plus uses about 30% per day. I do have the screen from about midnight to 06:30.

I would say hardly any improvement over a venu2plus using aid set to medium. I get 4 days.