I have spoken with numerous people lately regarding the value of their homes. In today's market, there are some property owners who are disappointed with their property's current market value. Many times, I hear the owners say that they have a year old appraisal, or a two year old appraisal that indicates that their home is worth substantially more than the estimate I give them.
Unfortunately, a 2 year old appraisal is useless in estimating value today. Market value is driven by the most current comparable sales data available. Several years back, an appraisal from 6 months prior may have been valid, as the market was far more stable at that time. But with the economy and housing market in a very precarious position, the appraisal's length of validity has probably been reduced to a very short time frame.
This does not mean the appraisers are wrong. They can only estimate the property's value from "historical data". They cannot predict the future.
So if you want a fair and accurate appraisal of your home, it needs to be as current as possible. The market seems to change every day lately, so the more recent the analysis, the higher probability for accuracy.