Windows Phone Thoughts: How Often Do You Willingly Hard Reset?

Ed posted a question a few days back asking how often people with WM 5 machines were subjected to unwanted hard resets. While I was one of those who hasn't ever had my WM 5 machine rebel against me with a hard reset, it got me wondering - how often do we willingly hard-reset our devices? Aside from ROM updates or bad apps, the only real reason I see to do this is to rebuild from scratch for maintenance purposes. While I used to re-format my Windows machines quarterly to get a fresh start, this slipped to twice a year and now yearly - and I feel my WM devices are going much the same route (Less voluntary hard resets now than ever). So how often do you hard reset willingly - and why?