Joe,
Butts have a pretty wide range of "done." I have experimented with different temps, over the last several years, and have found that the upper 180s to the really low 190s is perfect! Here's the deal: They are unpredictable, so no one can tell you
exactly how fast they will rise out of the stall. But, once you do see it start to rise, as it comes out of the stall, you can rest assured that the real "work" is done! The stall is where the internal fat is rendered, and the meat is tenderized. As the temp climbs out of the stall, go ahead and wrap/rest it from 188 - 192. The meat is just as tender as your 198, and more moist! You can tell by the feel, if you press a finger in it, that it's very tender and done.
Pork butts are just not that sensitive to temperature, once the stall is done! This is one of the reasons it is the perfect smoke for folks new to BBQ! It makes anyone look like a true "pit master" to their friends and family!