Berkeley - San Juan Islands - Boston via the Pacific Coast and Northern Tier routes took me 80 days, which included a five-day side trip to Yosemite and a three-day side trip to Minneapolis. Not a fast rider, usually at the back of the pack on club rides, I think 85 days will serve you well.
You are wise to consider shortening the route rather than racing through it. The memorable times happen when you stop for something special: scenery, a hike, county fair, etc. No one comes back saying how much he loved watching the road ahead of his front wheel.
My own best memories include the big ones: Yosemite Falls, Going-to-the-Sun, Waterton Park, and--surprisingly--three hours with a bunch of little reservation kids at their bicycle rodeo. After testing whether a fully-loaded touring bike could match their 16-inchers at weaving among the traffic cones (it could), we had a great Q&A session about riding across their state and the country.