I bought a new Roku Voice Control remote because my old one was draining batteries every week with little use and no Voice Control use. I have tried to restart, re-pair, and settings to pair with TV. Voice Control did not change volume either. Remote will power off/on the TV.
Device: Roku Express 3900X series
Update: 10.0.0 build 4195-51
Old remote: Voice Control RC-AL2
New remote: RC-EL1
Old remote controlled everything on TV but drained brand new batteries of every brand once a week. I checked for the update on device and it is up to date.
Remotes with power/volume/mute buttons connect to the Roku via Wifi-direct over the same wifi channel used by the Roku to connect to your home network. If you have a lot of congestion on this channel from nearby routers, there is some indication that this causes the remote to work overly hard to sort thru the conflicting signals on that channel and thus drain the batteries quickly.
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, 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 may work best. Also, reducing router bandwidth from 40 to 20 kHz may also reduce interference.