What sort of rate do people usually expect for tomato seeds?

I usually grow Sun gold (F1s) and get 95% - 100% germination success -
and all germinate within 2 weeks max?

But I am trying a wider selection this year.

Does heat (from underneath sand bed) make much difference do you think
to success rate? (I am not using one this year)

How long would you leave it before you would say they're not going to
germinate now?