I have said this for years that Seaham cannot sustain 3 cricket clubs. Just up the road, in the same postcode, is Murton CC. 8 teams to put out on Saturdays, plus scorers, officials, committee personnel, provision of teas, etc; etc.I think for Seaham Harbour it's asking too much off them with both Seaham Park and Dawdon little more than a stone throw away to put three teams out to play all afternoon.
In my experience I think third team cricket should be on a night over a short format who don't take it too seriously and want to enjoy the game.
Asking third team cricketers to give up a whole afternoon is too much imo and the longevity won't last.
Leagues, and clubs, will have to be more flexible. Allow clubs to compete with one team. Allow clubs to "loan" players.
Sundays are, generally, less of a problem. South Hetton, for example could not put out 2 teams on a Saturday, but had no problem putting out a Sunday team and a midweek 3rd team.
Saturdays are the problem for some clubs.
The only alternatives are clubs "merging" or clubs folding !