Bella Bella to Prince Rupert is probably the longest stretch on the Inside
Passage, although you may be able to get fuel at Hartley Bay, maybe 90 miles south of PR. If Hartley Bay works, you can travel the entire Inside
Passage with the longest stretch being about 153 nm, from Petersburg to Sitka.
But if you want to do some of the best sightseeing without planning so much around fuel stops, you would prefer at least 200-250 nm comfortable range. For example, between Petersburg and Juneau (135 nm) you might wish to visit the Tracy Arm (beautiful fjord with fabulous glaciers), which would add at least 50-60 nm to that leg. You'd need a similar range to enjoy the beauty and shrimping and crabbing of Hoonah Sound (a detour off Peril Strait on the way to Sitka). Or to explore Glacier Bay with much more wandering than just going up to the Margerie Glacier and back.