Heat is maybe the biggest uncontrolled enemy of tire wear (well, maybe alignment, given the same driving techniques). Going faster means more heat because of more friction, primarily because of the higher rate of flex as the tire rolls around and deflects. This generally means a need for a different tread and rubber compound and sometimes, stiffer carcass. Also, some of the higher speed rated tires come with a shallower tread depth when new, which helps prevent squirming and the resultant heat, but also generally means a shorter overall life before it gets too shallow for safety.
While not a perfect system, the rating provided on all tires sold in the USA will give you an idea of the relative life of any tire. You can look up the genesis of that rating, but it is based on a 'reference' tire's wear, which is rated at 100. Anything higher, such as say 400, means that tire should last 400% (4x) longer than the reference tire. This is not a guarantee of longevity, as who always drives like that reference?! But, it good for comparing longevity between numerous different tires.
The stock 19" tires have a Q rating, or a maximum of 99mph. The 20" are rated S, at up to 112mph. Running a tire faster than the rating will shorten its life and could damage it, potentially catastrophically. It's nice to have a little margin for error, but there are always compromises.
Both the 19" and 20" tires prior to those for the i3s are rated at 440, which, in the scheme of things is pretty good. You'd have to look at those on the i3s to see how they're marked...