Event tags concentrate a small, highly engaged audience into a narrow window. That is their strength and their whole limitation.
Pick the tag early and pick one
Event tags fragment badly. Three variants of the same conference tag will compete, attendees will split across them, and nobody gets a usable archive. Decide the exact string weeks ahead and put it on everything — the site, the tickets, the slides, the badges, the email footer, the signage.
If you are attending rather than organising, find out what the organiser is actually using rather than guessing. Guessing is how fragmentation starts.
The timeline
Three to four weeks out. Announce the tag. Use it on every promotional post so it has content on it before anyone arrives.
One week out. Anticipation content — speaker previews, packing, setup, behind the scenes. This is when people searching the tag are deciding whether to care.
During. Post live and post often. This is the entire point. Real-time content in an event tag reaches people who are actively watching it, which is a level of attention you cannot buy at other times.
Within 48 hours. Recap while the tag is warm. After about a week it is cold and the recap performs like an ordinary post.
Product launches
Same structure, longer runway. Seed the tag during teasing, peak on launch day, and then decide deliberately whether to retire it or keep it as an evergreen product tag. Both are valid; drifting between them is not.
Combine event with category
The event tag alone reaches attendees. Event plus category — the conference tag plus your discipline — reaches the subset of attendees who care about what you do. That subset is where the useful connections are.
Retire it cleanly
When the window closes, take the tag out of your rotation. Leaving a dead event tag on unrelated posts is the tagging equivalent of leaving the decorations up.