This year I have had good germination rates with most of my seeds. In the case of the tomatoes (which are easy to keep track of) it was 100%. Likewise, all but one of my Broad Bean seeds germinated - and both of its replacements! It's not so easy to judge the germination rate of smaller seeds sown in bigger quantities, but I'm very satisfied with these:
Those are Calendulas, from seeds given to me last year by Mike Rogers (aka Flighty), who writes the blog "Flighty's Plot". Mike sent me a very generous quantity of seeds, and I didn't sow them all last year. These ones are therefore about two years old, yet they are still obviously very vigorous.
These Chives are the ones from the cheap pack I bought at Wilkinson's. No germination problems here either!
Likewise plenty of Thyme seedlings have come up.
When sowing seeds I always sow a lot more than I really need, so a less-than-100% germination rate is seldom an issue. The exception is when I'm sowing F1 seeds, because packets of those normally contain only a very small number, and cost a lot of money. I generally sow F1 seeds individually, and monitor them very carefully.
I wonder what your opinion is of using "old" seeds? I think seed-merchants try to maximise their sales by trying to persuade us that seeds have a short shelf-life, but (with certain exceptions) I remain unconvinced. I regularly use seeds from packets opened two or three years previously, and sometimes much older than that. I'm still using some Chicories from a pack with a 2009 expiry date! The seeds with the shortest viability are supposed to be Parsnips. Most people think you should use fresh Parsnip seeds each year. I would normally not have much hesitation in using the previous year's seeds, but I would probably not use Parsnip seeds from two years previously.