Winter range drop worse than I expected?

Picked up my EV in spring, so this is my first real winter with it. I knew cold weather would hit range, but seeing the actual numbers is a bit of a shock. On motorway trips with the heater on, I'm getting maybe 30% less than the summer average. I know preheating while plugged in and using seat heaters helps, but I'm still adjusting my route planning. For those who've been through a few winters already, does the range loss stabilise as the car learns? And how much do winter tyres actually affect efficiency? Curious if my experience is typical or if something might be off with the battery management.