Writing over it is NOT recommended. The bar-coding that is printed on the label is what gets scanned, and many times, that's what does the sorting. So if it's a matter of a street name being wrong within the same zip code, maybe that's ok for that purpose, but if the zip is different, overwriting is simply looking for a delay in processing.
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).