I hand out a lot of rumors in my Felltower game.
How current are rumors?
Some Rumors Age
Some of the rumors in the game are time-limited. They provide information, probably old by the time you hear it, about something that is subject to change.
Oddball "I'm calling you from a café about 10 miles south of Mesurier. I wondered if you could do me a favor?"
Bellamy: "Mesurier? I got a map here someplace that says we haven't even captured that place yet!"
Oddball: "Yeah, so I heard. Everybody seems very friendly."
- Oddball and Bellamy, in Kelly's Heroes
It's usually easy to spot these. They refer to current events, recent happenings, and the actions of people who may come and go. They may age (and I'll take unheard but now aged rumors off the list, if necessary.)
Some Are History
Some rumors simply refer to the past. They don't reflect any current situation. They age, per se, but the information was already old. Rumors about the history of Felltower, of past adventurers, of lost civilizations and races, etc. refer to events already past. They may turn out to be false or too old (the lost sword was found, the dragon was slain, etc.) but they provide a basic understanding of the world of the past.
Some are Timeless
Some of them refer to foundational elements of the world or the game. They don't actually come with a time limit. Rumors about monster weaknesses, strange varieties of magic items, mystic pools, etc. are like this. They probably don't change.
"It's timeless, like a fine watch." - paraphrasing Zonker Harris (IIRC)