Why do you put the fleece on? If the canister is as warm/cold as the environment, covering will just cool the canister down even more. Canisters get colder in use, now you are insulating it against the 'warmer' outside.
True. If the canister is colder than the surrounding environment, you don't want to cover it. If the canister is warmer than the surrounding environment, then you do want to cover it.
HJ