I repaired and drive an 07 TCH which has leather and seat heaters, and own an 09 with cloth and no seat heaters. I'm in Canada, now in Vancouver, and from Winnipeg, home of the block heater.
My experience has been that leather seats have more thermal mass to the covers, and will feel "cold" longer than their cloth counterparts, I recognise you're comparing Cadillac to Camry, both leather, but all seat heaters in my experience use a thermostat to modulate the temerature. It's a function of the thermostat, and it's location on the pad. Some aftermarket heaters may heat longer, but you may have a time of coupling with the OEM switches. I imagine a swap of heating pads may satisfy your wife's behind, check with your local car upholstry shops..
Regards,
Roy

 

Roy,

Thanks very much for this good information and insight; especially the bit about the location.

I may open up a seat upholstery and investigate whether the thermostat is too close to the heating element.

(After I get one of those little round things !)

Jack

 

Our '09 TCH's heated seats were just right during this brutal winter season in SE PA.

You wanna talk about weak Toyota seat heaters - the ones in our '04 Sienna XLE LTD were totally USELESS. This was a definite flaw - many people complained about it on the Sienna message boards.