Assuming that 1.4 was supposed to fix them, how long does it take?

If you look at the bottom of the first page of this link and the start of page two, there is a short discussion ash piles which you may be interested in.

http://www.gamesas.com/topic/1344864-patch-141904-is-available/

It will take 30 days of waiting for the 'clean up' scripts to take effect.

Is that confirmed?

Someone here said they waited 30 days and the "named" ash piles still remained.

Yes. And most likely, this is intentiional, as it is a record what has happened to named NPC's. This wont cause any savegame bloat because there is only one instance of named NPC's, and so there will only be one ash-pile for that NPC. The ash-piles for generic enemies (like bandits, bears, etc) will be cleaned up, because generic enemies can respawn. This means if those respawned enemies were also turned into ash-piles, then the game would eventually fill up with ash piles. Thus, the fix only applies to the ash-piles from generic enemies.