So called professionals

A lot of seeds last much longer than they say on the packet, it's mostly things like onions and parsnips which have a big drop off in germination rate.

I don't disagree with what you are saying tmtt, but I think I came across a reference to someone growing record breaking onions from a packet of seeds that had been in his jacket pocket for 7 years, similarly with what Vinny says about the old parsnip seeds, though as a general rule the germination rate might drop, you can still get a good crop from old seeds