They have been getting updated. Not quite every day, but at least 2-3 times a week right now. I have a note on the main snowcover page it reads:
If the maps are showing an old date, you need to force the page to reload. To do this, you can do one of all of the following:
1) Hit and hold the shift key and click on the reload button on your browser.
2) Hit F5
3) Right click on the map, choose to view map in new tab and then use technique(s) 1 or 2 above.
You can also go into your browser settings and clear your cashe.