Scheduled reminder email: emails sent for ancient events

Forum post http://forum.civicrm.org/index.php/topic,23423.0.html describes the issue.

Setting up a Scheduled Reminder email leads to many emails being sent to participants of non-current events. (A trip down memory lane for the nostalgious?

The forum thread identifies a fix which is creating a time-window in which these emails can be sent. There is some discussion about the best size of this window, given assumptions about how often jobs are run.

My own suggestion for a fix would avoid making assumptions about a time-window. Simply record a timestamp of when the civicrm_action_schedule was created. Then the email is only sent if the calculated 'date to send email' is greater than this date. If the user specifies a fixed date, only send the email for events and activities that start after the timestamp date.