Is this normal??

Hoping that some of you very nice people can help me out here.
during this cold-snap, I, just like most of you, have been setting the heating on 'program' & leaving it running for 15min or so, then its nice & clear & warm upon setting-off at 0600!!
Now we all know that 'program' switches front & rear screens, mirrors etc.
So far so good.
Now then, whilst waiting for 'er indoors this morning, I rolled down the window & brushed frozen snow from the mirror top, then I casually ran the back of my fingers down the mirror-glass, WOW, IT WAS RED HOT!!! So was the other side!
BUT, the 'Program' switch was OFF & the heating was set to 'HIGH'
So, kind people, do the mirror-heaters come on when the outside temp is low (it was showing 2 deg) at 0900 in the morning, OR is my wonderfull RR electrics throwing another wobbly!!
Also, do the mirrors normally come on, on 'program, front-screen or rear-screen, 'cos both screens can be individually switched, but NOT the mirrors!!
Anyone care to try your vehicle & tell me your results?
Ta.

If I read the manual and RAVE correctly the mirror heaters are actually permanently on, but red hot doesn't sound very good.

Ok, OK, so 'red-hot' may have been 'slightly' over-exagerated!!

It was cold, so they seemed like it!! Thanks.