I'm currently on Mat Leave but when I was working we weren't made to attend just "strongly encouraged" so i would try and attend at least one a year (we used to have one each quarter) and maybe for the second one just pop in for a quick hello and leave, this was enough to get rid of the guilts from other workers and from myself as well. Our functions were always fairly informal though so that was easy enough and I always left before things got messy.

HTH