how long is my survey good for?

It depends on how the survey is to be used and if there has been any changes to the property. If you intend to use for closing or financing purposes, different institutions usually have their on criteria on the age of a survey. If you are trying to use it for building or permitting, the age of the survey would vary dependent of the part of the country or state you are located in. The best way, is to
check with the entity you are dealing with.