I would continue the time frame through 2008, but would be very careful of 2009 & 2010 models, as that was the time leading to the bankruptcy. Any 2010 model with the Navistar sticker by the entry door was either built under the eye of Navistar or they QA'd the Monaco built unit and gave a warranty on it, so it should be OK.
The RR4R chassis on the lower level models from 2002 till bankruptcy, is not a chassis of choice and has a serious chassis trailing arm safety recall that you as the owner will have to address. It also is a very rough riding chassis without lots of upgrades.
The RR8R and higher level chassis are the chassis of choice with no recalls and is a good riding chassis. Personally, I would only look at the Endeavor and higher level coaches, but that is only my opinion. The Monaco line is a twin of the HR line, with the Diplomat being the twin to the Endeavor.