Yeah, I know these type of connections well. I found in my 30s that I was relied upon professionally (by work colleagues) and socially (by people who treated me, at first, like a valued friend or acquaintance). All my life I have been able to problem solve and succeed in cutting through difficult situations and crises.
At work, I was asked to lead 'delegations' and campaigns. In public situations, I was asked by others to lead co-writing submissions or to speak to mediators on others' behalf. In social situations, a lot of the people I knew and mixed with wanted me to be the ringleader or group spokesperson or negotiate for them.
A long-term friend, Barbara, eventually said to me, "Iain, you really learn to say NO more often or at least to tell people to start to stand up on their own behalf. People have learned that you're a can-do type of person and they make a beeline to you. What does any one of these people offer to do in return for themselves or for you. No one takes back your load ... people find out that you are energetic and organised and let you do things for them. You do you own work then tire yourself more by solving bits of theirs. You get verbal thanks, of course, and occasional fawning flattery but, ultimately, you are eating into your rest time and family time. Please, take my advice and become more selfish for your own good. If you can do more than others, they will tend to use you up if they can."
It took a while but I realised (eventually) how right she was. I pared back my time-slicing and I did learn to put many more NOs in my vocabulary and public personna.
= = =
When it comes to friends like yours, the ones where the effort of connections or realtionships becomes loaded for you while the others 'coast' along.
I very much felt for you when you scored a pre-invitation to the 50th which, later, never came to fruition.
People will often be prepared to lie directly or by ommision. They might find you convenient when they need you or need you to organise a thing they like.
ANALOGY: They seem a lot like 'fair-weather" supporters of a sports club ... you see them when the team is winning or having an occasional purple patch BUT, when the team has a succession of defeats or setbacks, they'll stop attending the game.
Time to rethink your connections, I'd say and MAYBE, just maybe, let the taxing relationships die off naturally.