I have a Mi box and the batteries on my remote drain out in about 3 days. I'm not sure if it's a hardware problem on the remote or some sort of software/setting on the box that constantly keeps the bluetooth connection on. Did someone have a similar problem on this or any other box ?
Either you have a hardware issue or crap batteries. Go buy these if you suspect the latter: https://www.ikea.com/us/en/catalog/products/90303880/ . They are made in the same factory as Eneloops and have suspiciously similar discharge characteristics.
I don't really know if they are supposed to last a long time. I just remember I was surprised the first time they were drained and I bought a Harmony remote the next day to use IR instead of Bluetooth.
I didn't have that problem before going to IR, but it happens on some devices, generally it's was a battery issue.
I bought high capacity panasonic rechargable batteries and that would last a whole lot longer. Then I always just swapped out the batteries when needed (not having to throw away and buy more)
I have mine for a couple of weeks, still 96%. I'm using the batteries that came with the mibox 3.
The battery on these for me (3 boxes) lasts a long time (6+ months), even with daily use. I don't think there are any settings that you can change, so not sure what is wrong with your one. I did buy a cheap (non-genuine) PS3 bluetooth remote years ago and it used to chew through batteries every few days (do you have a third party remote?)