Three months is a fair assumption that it's a no.
However, I once did get a response asking for a partial after 7 months. I never heard another word after sending the partial. The agency in question blogs regularly and is quite proud of themselves. (Not the lovely Kirsten Nelson.)
I also got a request for a partial after 6 months, along with, believe it or not, an apology for the delay. I had signed with another agent by then, though.