[ASpring]

I don't think there are really guidelines on 'how often' UX research should happen. Ideally it is integrated in the development cycle and something like this is found in a usability test and fixed before deployment. Usability testing and UX research are a continual process.

[bryanrasmussen]

right, unfortunately in dealing with governmental bodies it is best to point to something in a document written by someone with some apparent expertise in a matter that would say something like 'Usability is something to be continually evaluated, in order to have get the best and most accurate view of an application's usability for its target group it is best to have a semi-annual testing regimen based on analytics of the actual application usage in between the last system improvements...yadda,yadda,yadda'