I have a Selle Anatomica Titanico X and they do stretch a bit. Mine has stopped stretching and was comfy out of the box and it still is. I regularly ride in the rain, leave the bike parked in the rain and out in the sun.

That being said I like it better than my previous B17. After about 12-13 k my B17 started to be less comfortable but as I said i ride in the rain , snow etc. I covered my Brooks most of the time.

I didn't pay retail and if you watch they go on sale often. The thing I like about Selle is that I can get it recovered for half the retail price if it wears out as my B17 did. YMMV.