There are a bunch of weird smartwatches that get pretty close to this - for example, the Amazfit Bip S Lite claims 30 days of battery with a similar transflective screen (albeit I think the heart rate monitor drops to once every measuring 5 minutes in battery saver mode).
Similarly, the Withings Scanwatch claims the same, although as a hybrid smartwatch, it is not driving such a power-hungry screen.
I had the OG Bip and got extremely close to 3 months at one point. Unfortunately I don't remember if I had the HR set to 5 minute intervals but if it was on, I think that was the setting.
Even with 1 minute intervals though, battery life was absolutely stellar. I'd often lose my charger, and in few days after I saw the battery dropping/low battery alerts, I'd find it too (before the watch died)!
Similarly, the Withings Scanwatch claims the same, although as a hybrid smartwatch, it is not driving such a power-hungry screen.