This made me think... what if I manually send notifications about big yearly events to the users using my
telegram notification bot (~1000 users)?
For exemple, icopress' yearly
Bitcointalk Community Awards, the Bitcoin Pizza competition etc...
I could send a one time survey asking if they want to know about these big events (which happens like 3-4 times per year, nothing too spammy).
Probably this is a good idea. I am sure that your Bot users will be happy to get such notifications. One thing I understand is, that whoever using your bot, cares about the forum and its events. If someone does not care about the forum too much, they won't use a notification bot to get instant notifications for mentions, merits, and other things. So, with a survey or without a survey, you can start giving notifications for such events.
I remember how you tried to fool us on April 1 and I don't think anyone feels disturbed even though you messed up with the message. So, I would ask you to start doing that if you can do it without massive hassle.