How often do you factory reset your phone?

No, we aren't talking restarts here, which big software version updates do for you anyway, but actually resetting your device, and starting with it as a newborn child, curiously looking around and exploring the world.
Granted, it does warrant some total backup before you do it, but it can potentially get rid of the lot of problems plaguing your handset, and is sometimes even the only option when things go terribly wrong, so do you do it?
How often do you factory reset your phone?
Never
22.43%
When I feel it's getting sluggish
44.7%
Only before I sell it
32.87%
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