If you are happy with a little fettling, you can make fewer bikes works quite nicely. By reducing your two MTBs to one, I think you would avoid future costs rather than save loads of money now though.
I ride about 3,500 miles a year and do a lot of different types (MTB, touring, commuting etc). Some people would have a different bike for each.
However, storage space has become the biggest decider in my bike stable as our kids have grown – so I have “just” two bikes: a Cotic Soul 275 and Surly Straggler. (That said, I’m planning to get a Brompton soon!).
My Soul is set up with a rigid fork and singlespeed from November-March and then with 1×11 and boucy forks when it’s dryer. I have two sets of wheels for the Straggler: 28c on lighter wheels and 41c knobblies on heavier ones.
The Soul gets ridden for all sorts of riding and it’s just fine – as I suspect your HT would be.