I think setting an expectation that members host an open evening at twice a year if their circumstances allow it is entirely reasonable. And that anyone who can’t do it helps in other ways instead. @peter_hellyer is working on a welcome message at the moment and we could include this.
I also think weekly open evenings are a good thing. If people had to wait for a month to come to an open evening they would just turn up at random times which would be less successful for visitors and for whoever happened to be in the space at the time. I think it’s worth persisting with this.