#2 & #3 synchro's take a beating in general. I'd say ease up on the 3/2 downshifts or you'll lose the #2 synchro altogether.
Personally, when I do a 3/2 downshift, it's at about 20mph. Downshifting, as a habit, saves break pad wear but does wear on the clutch disc. What's easier/cheaper to...