Regarding wheel durability -- lot of posts in several threads about how some of the new generation softer wheels (Soft Sliders, X-Formula, Dragons) wear out hella fast.
Just to chime in: I've been on 55mm X99s for a good while now (several months, 1-3 sessions per week on average), and skated a lot of very shitty and crusty spots (with some smoother parks thrown in the mix), combined with repeated powersliding on my home stretch which is a fun crusty downhill.
Just calipered the wheels yesterday, and they're all still at minimum of 54.5mm, no joke.
I know, I don't skate every day, but still, for me this equals as pretty durable for a "softer" wheel.