I've been following this thread with great interest, because I had the same questions about flex. I've got 6-year-old Tecnica Diablo Sparks, which have a 70 flex. I got them when I was still just becoming an intermediate skier. I don't have any complaints with them, just thought that I could "up my game" with some new boots. Plus, I just bought new skis, so what else can I buy?
I had been thinking that I should look at 90 flex, because: (a) it wouldn't be such a huge change from what I have now, so it wouldn't be a big adjustment in balance; (b) I only weigh 150 lbs., so I don't need monster-stiff boots; and (c) my kids and I ski a lot in trees and bumps -- we're not doing slalom racing. But now, reading this thread -- and knowing that whatever boots I get will be the ones I use for another 5-6 years -- I wonder if I should go up a notch to 100. Any thoughts?
A related question: is it better to buy after this season winds down -- to get a good deal -- or is this coming year's crop of boots looking like it will be so awesomely innovative that I ought to wait until next Fall?
PS-1: Yes, yes, I know, go to a brick-and-mortar ski store, work with a reputable boot-fitter, do whatever they say, etc.
PS-2: I think I'd like the boots that allow you to switch to walk mode (e.g., Tecnica Cochise, Atomic Waymaker, etc.). The kids and I don't (yet) do much backcountry hike-to skiing, but I think walk mode would be cool for going through the lunch line at the base lodge, and sometimes it's a long way to the restrooms.... Thoughts? Recommendations? Are any of these walk-mode boots slated for "awesome innovation" this coming model year, so that I should wait?
I would likely push a little higher 110, as you will likely be getting better (stiffer skis) soon that will match you ability. That upwards improvement usually drives an equipment change as the old actually hinders further development (as the equipment actually behaves as your making a mistake when you are actually doing it correctly with a lot quicker and with more power).
My recommendation is always go a bit higher than you are (except when starting) as you will grow (experience wise) into it quickly.
My recommendation to friends and family always has been good beginner/intermediate equipment, next step good intermediate/ADVANCED equipment (little biased towards the advanced).