Residential Properties: Appraisal Frequency??

[Meghan Chomut]

Is there a general rule of thumb for how often I should be getting my real estate appraised? So far I've just been using my own judgement on what they are worth (I am not a real estate professional) by looking at comparables in my region.

But then, I was thinking that businesses look at their valuation annually, and I'm wondering if I should do the same.