How long does a Hireling work?

Heroes are able to get the service of hirelings; these can be mercenaries, laborers, skilled artisans, etc… A mercenary or bodyguard will work 18 to 24 hours for the player during adventurers. But what about a local smith? If you pay a hireling to do some artisan work for you, will they work 16 hours per day or only 8 hours?

After all, most D&D games are happening in a medieval setting of time. People didn’t work only 8 hours per day. It’s interesting to know since a player skilled in smithery can make a progress of 5 GP per day (during a downtime of 8 hours).

If hirelings were to work 16 hours per day, then we could calculate their daily progress in crafting as 10 GP per day (or 7.5 GP; should they work 12 hours). From my understanding, a PC could have a downtime of 16 hours.

It’s nice to know, since equipment could be made faster and the daily cost of a hireling would go down by half.

Edit: I would also like to add the thought that an adventurer could be a patron of a smithery with a skilled hireling. Would this person work for the player with a 5 GP or 7.5/10 GP daily progress? 16 hours of work with 8 hours left to rest seems harsh, but was it that uncommon in the medieval time?