Seasons

Six to twelve weeks, and twelve is the ceiling. Shorter than six and half the field never gets three matches in. Longer than twelve and the standings stop feeling live, because a result from four months ago is still holding somebody's rung. Publish the start and end dates before anybody joins.

The other option is to run the ladder open-ended, with no end date. That works for a group that plays all year, but it puts the whole weight on inactivity decay: without a close, nothing else clears out a rung somebody stopped defending. Pick open-ended for continuity, a fixed season for a finish line and a playoff. Season rules.

Carry them over. A cold start every spring throws away the one thing the ladder built, which is a roughly accurate ordering of the group, and it forces everybody through a round of pointless mismatches to rebuild it. Carrying over does concentrate an advantage at the top, which is what the playoff and the level bands are for.

Ladders need reviving far more often than they need founding. What works:

1. Find out why it stopped. It is almost always one of three things: the organizer burned out, the deadlines were never enforced, or the group got too thin to produce matches.
2. Cut the roster to the people who actually played. Do not reopen with the old list. Reopen with the eight who showed up.
3. Start a new season with published dates, rather than resuming the old standings mid-air.
4. Automate whichever failure killed it, because willpower already lost once.

If it died on admin, start a ladder and hand the deadlines to software.