With the frequent complaints about battery life we see here, I've started tracking mine by putting a small slip of paper with the date on it into the battery compartment when I install new batteries.
My most used Roku is the Streaming Stick+ (3810) in my living room.
In several sets of batteries I receive 2.5 to 3.5 months per set.
There is some evidence that one cause of battery drain for those with point-anywhere remotes that connect to the Roku via WiFi-direct can be use of a router channel that is crowded by nearby routers using the same channel. It has been suggested that the remote has to work too hard constantly sorting through the information packets from other devices using the same channel and it may accelerate the battery drain.
If you have access to your router's setup, try configuring it to use a different WiFi channel to see if this helps the situation.
In the 2.4 GHz band, channels 1-11 are supported. Channels 1, 6, and 11 do not overlap each other and so give you the best chance at reducing congestion, so try each in succession, although depending on what channels your neighbors are using other channels in the 1-11 range may work best. Also, reducing router bandwidth from 40 to 20 kHz may also reduce interference. I use a wifi analyzer app on my cell phone to determine the channel with least interference.
One more point for those readers who have one of the remotes that has an earphone jack for remote listening:
The earphone amplifier in the remote is activated and more quickly draining batteries whenever something is plugged into the jack, even when you are not streaming anything.
Make sure you unplug the phones when not actively listening.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X