I think the current time limit is 30 seconds.
Generally I'm led to believe the tags are there to stop people covering their arses when they get contradicted or some such. A reasonable time frame for that, even in a thread going at ridiculous pace like an Ashes match thread, would IMO be at least 5 minutes.
Wouldn't be as bothered by this if honest grammar Nazis like me didn't get lumped into the same category as blatant fact-wranglers who then claim they got misquoted. It takes a bit longer than thirty seconds to correct a split infinitive or put a semicolon in place of a comma, specially when posting from a tablet.
Or, at least, add a pithy diss of Broad that you thought of one minute later. It just looks so bad (at least to me) when I have one-sentence posts flagged as 'MESSAGE EDITED' simply because autocorrect felt like being a **** that day.
Thanks for reading.