The seed companies have no idea where the seeds will be planted, how they were stored, and under what conditions of light, soil, moisture, temperature, and so on they will be subjected to. Any statement about germination times (when something breaks the soil surface, in my opinion) is an educated-but-still-wild guess.

As an example, toms I seeded a month ago in the house were all (but one) sprouted in four or five days. In December that time, under heat, would be eight days or so. But they'd be timed pretty consistently across the tomato varieties.

With reliable seed companies you can count on some sprouting consistency in the bag of seeds. Planting seeds in pairs or threes helps even out sprouting variations as you get to choose which ones live. In your case is there a penalty (like death, fungus, etc.) for dealing with the seedlings as they emerge verses waiting to do something with them all at the same time?

Ah, I hadn't thought about those issues, but what you say makes a sense.

Regarding your question about a penalty, I'm not 100% sure. I am using a seed starting kit from Burpee, which has a plastic "germination sheet". I am supposed to cover the seeds with this until they sprout, and then remove it. Since some have sprouted, I guess there might be a penalty either way—I don't know if keeping the sheet on will injure the plants that have already germinated or if taking it off will prevent the ones that haven't come up yet from possibly germinating. Do you think I should leave the sheet on?

Take it off. The covering is normally removed at the first sign of germination ;) Think, bird in the hand. You want to protect the seedlings you do have, and leaving the cover on will increase the possibility of damping off. They need some air circulating. Chances are more will follow even if you have removed it, it only helps, the seeds aren't dependent on the cover.

Gotcha, will do! Thanks for the help.

It is only an experiment, but I do hope that the germination rate ultimately gets a little higher. I planted 12 seeds, and so far only 4 of them have sprouted. I thought I might double that (8 seeds). I know that it's not an exact science, though, so not sure if that's an unreasonable expectation.