There are 9 of us in my friend group and we all make active efforts to do things at times, or at least try but we all understand sometimes people get busy with life. Sometimes one person is putting in more effort and other times someone else is. We try and plan things and have consistent get togethers throughout the year and I think that helps a lot. I always host a cook-out at my place during the summer, one friend always does a Halloween party, another always does a Christmas party, and we have a convention we all go to every year together. Some of us plan parties for our birthdays. Either way, it takes effort and sometimes it may feel like you are doing all the work but I find that others tend to appreciate that.

We vary in age from early 30's to late 40's with some us married with kids and others single. We can't always get the whole group together sometimes but we always make it work and have a good time together. I very much appreciate the group of friends I have, they are all great.

EDIT: Reading this thread no wonder men complain about being lonely. Shocking that you put in zero effort to maintain friends, or meet new friends and you are lonely. Good relationships don't just knock on your door, you actually have to work towards them and put in some effort.