Logstash filter basted on log file age

[Badger]

Assuming that @timestamp is set to the original date of the log you could do something like

ruby { code => 'event.set("[@metadata][age]", Time.now.to_f - event.timestamp.to_f)' }
mutate { convert => { "[@metadata][age]" => "integer" } }
if 172800 < [@metadata][age] {
     # Alternate throttling code
} else {
     # existing throttling
}