Back in the day I had several 2-3 word domains with plural in the middle. But I avoid them these days except in rare circumstances, as I've never been able to sell one.
There are exceptions to this:
PeoplesChoice.com - when the term is possessive "people's choice"
BasicsMarket.com - In rare cases where a word is normally an adjective but made into a noun (substantive words) the plural works better. For example custom motorcycles, which then is mainly referred to as "customs" and in this case the plural is the preferred word. So CustomsFactory.com would be good in this case.
PartsFinder.com - In rare cases, similar to the above, plural versions of nouns are universally more common than the singular version in a particular industry or context. For example, "I'm going to the auto parts store" rather than "I'm going to the auto part store". Along the same lines, you don't go to the "groceries store", you go to the "grocery store".