My company makes a big point in work-life balance. We can meet up in a bar to throw darts at most 2 times per year - anything more and we are impacting family time. Lunch is a good social time, but that is personal time and often better spent meeting with people not on the team (some always go home, some meet with old team members...) Your team should meet during your normal 40 hour work week (or whatever hours you work) for team social time.