Add to the stable or not

I have a similar kinda trails and situation like you..I got a new bronson a couple of months ago..and is a grate compromise for those long XC rides with a few good trails..the 5010 looks good for what you need also but the bronson will do more when you need it

have you thought about some of the new 120mm rear bikes out there for a little more distinction between your bikes? the norco fluid has been SUPER fun (i'm on a 29 but they make 27). review coming soon. i also just got a marin rift zone to try out (29, but the hawk hill is 27.5 with 120mm). only two rides on it, but also super fun so far. there's something about the zip and the pep these bike have w/ only 120mm on flowy terrain where a 150-160 bike would be a hog. they're like slalom bikes almost. both the norco and marin are budget-built bikes ($3k or less) so there could be more blingy options out there.

Spomers advise is on point. I have been in the same boat here in Whistler. Got a dh for the park, an sb6 for day to day riding, but we also have weekly xc races, and lots of big long epic days in the chilcotins etc. I have long longed for something like the yeti sb100, and would jump on that in a heartbeat if i was a dentist...
Your other option would be to get something just a little less plow specific than the spartan. SB6, new bronson, new stumpy, bikes that can handle nearly everything, but still scrub up nicely for long days. I currently just change out tires when heading for 3 days of backcountry riding and it works fine...

I have a 125mm Transition Scout and a 170mm YT Capra (soon to be replaced by a transition sentinel), they both get ridden a lot. the scout gets ridden on gnarly trails and flow trails but definitely cant keep up with the YT when it gets really rough. The YT never gets ridden on flow trails, it loves going fast, Im hoping the sentinel is better than the capra at both the gnar and the flow trails but will always plan to have a short travel rigs for more pedally rides.

I have a Giant Reign that has sat and gathered dust. I got an Intense Primer and found it was very capable and started riding it more and more. The Reign is basicly a park bike at this point unless I went somewhere with big hits but most everything else the Primer gets rode. I may not be as fast on it but a lot of the time it’s more fun as I am having to work to ride and not just let the bike plow through things.