Duration with in

In Shaetlan it is common to indicate duration with the preposition in, where StE has "for":

– The little red hen worked hard for thousands of hours to gather her material, without any help or even thanks, so once her cake was finished she had no time for the mouths that came gaping.

This is neither new, nor slang, nor sloppy speech. The use of in to indicate duration is attested in Old English since the 10C at the latest. Also, it is the standard way of expressing duration in the Scandinavian languages (cf. Den lilla röda hönan kämpade i tusentals timmar...), going back to Old Norse usage. It is likely that the use of in for duration was reinforced by Norn and is another old substratal feature that has remained hidden in plain sight.

PS: for those who don't know the story, "The Little Red Hen" is an American fable about the importance of hard work and personal initiative. When the hen finds some barley and wants to make some bread, none of the other animals on the farm wants to help her at any point. So she plants, harvests and mills it herself. However when the bread is finished the other animals are all eager to help her eat the bread.