A family of Microsoft word processing software products for creating web, email, and print documents.
As long as you are still in the same Word session, I would expect printer settings to be preserved. In other words, for Word to revert to the default printer (and its default settings), you have to exit and restart Word. Closing a single document won't suffice.
Others have reported that Word 2013 behaves differently from older versions with regards to printer settings. I haven't seen this myself.
Have you tried a different printer?