This is roughly what we have now. Twice a month we organise a company wide update/demo session on Friday afternoon with drinks and food afterwards. Most work in the office that day and use the day for larger in-person meetings.

Some people come in a few days a week in other weeks as well. Some really only come in those two days. A small number of people nearly never come in (always dial in). It doesn't seam related to travel time, more to personal preference for being out of the house / in an office.