Tucson, AZ to Bremerton, WA area: How quickly?

We do pretty much the same trip twice a year. South of Tucson to the Portland, OR area. The fastest we have done it was three days and more usual is 5+ because we sight see along the way. Portland to the Seattle area would probably add another day. Keep in mind that if you take the I-5 California route and are towing anything the speed limit is 55 MPH as compared to Arizona and Nevada where they are 75.