> If you do create the categories, make sure to have the year
> in them, such as [[Category:GenCon 2007]]. I think that
> would be preferable for both planning and archival purposes.
Indeed. So the templates should be like {{attends_GenCon06}}
{{attends_GenCon07}} {{attends_GenCon08}} with the badge reading "This user
attended GenCon in 2006" "This user is attending GenCon this year" and "This
user will attend GenCon 2008" respectively. Of course, after GenCon 2007,
it the template can be modified to the past tense, and everybody will be
automatically updated.