I think plant vigor starts with seed vigor.
Do plants from poorly/slowly germinating seeds, a month behind your others do well for you? I think normal healthy fresh tomato seeds should germinate in good conditions in under ten days at most.
New seed, new seedling mix in a new pot after ten days of no germination I would say for myself.
Exceptions could be made for old or somehow special seed in which case I think a pre treatment such as soaking in a dilute H2O2 solution or weak fertilizer would be a good idea and more likely to be successful.
Planting more than you need in order to be able to select the best plants right from the start is a good idea.
The best tomatoes come from the best plants that come from the best seedlings that come from the best vigorous fast germinating seeds.
KarenO