Spent many years living in the Yukon where there was virtually no pavement other than in Whitehorse. We have done the Dempster couple of times and love it. SLOW is the key. Take lots of time. As others have stated the northern gravel roads are 100% dependent on weather. We have been lucky both trips. If you get several days of heavy rain Ina row , it can mess with the road surface but as a rule it's pretty well maintained. Two ferry crossings but both operate pretty well. I'd plan on Six days travel time ( return) and probably a night or two in Inuvik. Inuvik is completely unique to any place else you will visit and worth a couple of days of poking around and walking.
We are planning a summer 2020 trip all the way to Tuktoyaktuk. As others have mentioned, a new all weather road opened in November of 2017. I'd like to give it a couple of years to settle in before we do it. There's fuel, commercial camping and services at Eagle Plains and pretty good services in Inuvik. There is also fuel at Ft MacPherson (when it's open ??). The scenery at both ends is kind of hohum but the high plains and mountain passes in the center are spectacular.
Happy travelling.