I (try to) have lunch every Friday at the Yin-Yue Restaurant. A fellow from COLUG invited me to lunch with his group, once, and I've been making an effort to attend ever since. Several of the other folks there have meeting for lunch every Friday for the last 25 years! The tradition started while they were in graduate school, and needed a break from studying ... the rest, as they say, is history.
Most of the group is older than me, and they're all certainly smarter than me, which is one of the reasons I enjoy lunch with them so much. They talk about all manner of geekery goodness, from aviation, to cryptography, to robotics, to general electronics. The professions represented are varied, and the accumulated knowledge and expertise is impressive. I listen a lot more than I talk, and I usually walk away from the table with some small bit of knowledge I didn't have before.