Last summer I did Christina Lake BC (that's the lake on the lower left of the map there) to Castlegar to Trail to Rossland and back to to Christina Lake on my 69" geared marinoni conversion. This was about 180 kms with 2500 metres of climbing over two big passes, the Blueberry Paulson and Nancy Greene.
Climbing was almost always fine; the descents were where things got tough. I would love to do more fixed endurance riding but have found various things got in the way of it over the last few months.