[bam80]

I did not realise remotes went to sleep as they are only transmitters and I thought they only use battery power when you pressed a button.

In IR case they are,
but RF remotes need power to keep the link up, and suffer additional delay when the link eventually broken(remote go to sleep) to set it up again (may be small though).

My batteries last a long time so I guess they all take a rest and go to sleep

Hope your T3 batteries do the same