Here is something I just tried, and from all indications - has worked.
I have tried everything including IPSW updates with no backup restore and nothing worked - I have many devices in active use and a lot of past devices I have donated on to family or sold. Many of these still appear in the iCloud pref pane on my Macs.
In my case and some others it appears to be an issue with Keychain/AppleId synchronisation, specifically I believe it to be related to how AppleId uses other devices as a form of MFA when you sign into iCloud on a new device and it requests the PIN/Password of another device.
In my case, my Watch and phone were going flat for a week by 3-5pm, where they would typically last over 24 hours before. Nothing I did stopped it, but I did notice various devices randomly requiring me to sign back into iCloud to "restore all services". This made me suspect it was AppleId related.
I got the main hint from noticing a MacBook running with fans on due to a process TrustedPeersHelper using a full core flat out.
Searching that process led me to this post:
https://www.reddit.com/r/MacOS/comments/dmbuj5
Based on some comments from that thread, what I did was:
1. Shut down ALL iOS devices
2. On Macs, I ran (first one deletes a database about trusted devices for the AppleId):
> rm -f ~/Library/Keychains/*/com.apple.security.keychain-defaultContext.TrustedPeersHelper.{db,db-shm,db-wal}
Followed by (which resets "CuttleFish" - can't find any documentation on this but I believe to be an iCloud service for syncing this database):
> tpctl reset
I then shut them down.
3. With all devices shut down, I booted a single Mac, and went to preferences and re-signed in as prompted (reseting the cuttlefish service seems to lose all the device trusts I guess - but doesn't actually sign you out of iCloud).
4. Once signed in, I reviewed the list of devices associated to the AppleId, and cleaned them out.
5. I rebooted the Mac and left it for 10 minutes to re-build the local database deleted earlier.
6. Booted another Mac and signed in and waited for its keychain to rebuild and rebooted it.
7. One by one, I restarted iOS devices, signed them back in from settings as prompted.
immediately my iOS devices are drawing a normal amount and TrustedPeersHelper on the Macs are using pretty much no CPU time.
It took a while for each device to settle down again, and the iPhone needed me to -look- at the iMessage settings to get it working again properly.
I don't know which part fixed it, but I did have about 10 old devices still bound to my AppleId that are now gone- fingers crossed it keeps working for me and helps others