Personally I don’t think the SSB2 progression has long enough SST efforts for building up to really long stuff. There’s some good info in the “Sweet Spot Progression” thread, but maybe something like 2x20 → 3x15 → 2x25 → 3x20 → 1x50 → 2x30 → 3x25 → 2x40 → 3x30? And then you can add 15 to 30m of Z2 on the end after those as well. I’ve found this kind of work to be really beneficial for longer distance efforts and having the muscle endurance to keep going for really long days.
Edit: here’s a link to the SST thread. There is A LOT of info there (2k posts) but I think this chart at the beginning is a decent starting point, work your way out from there to get to as long of a duration as you can in the time you have: Sweet Spot Progression - #2 by bbarrera