This season I sowed four Dr. Carolyn seeds in a 1" cell, alongside my others. The packs got bottom heat for about five days, until most of the cells had sprouted. I only got one Dr. Carolyn, but I figured I only needed one... they were pretty young seeds, three years old or less, but sometimes they just don't come up.
A couple of days ago, up came two more, late but healthy. Their sib already has a set of true leaves, and is thinking about more; this is about three and a half weeks after sowing. And that was with fresh seed and bottom heat.
Don't give up on tomato seeds -- like jokers, they'll turn up when you least expect them. I'd give them a month... if you're worried you won't have enough, sow a few more as well, and give away any extras you end up with.
--Alison
who was also waiting for Brandywine Sudduth and Olga's Round Yellow Chicken, sowed more during the wait, and now has LOTS. The extras will go to the college plant sale...