Growing out of date seed- the results are in

Did you chit all the seeds? last year I chitted sweetcorn 4 years out of date and all were successful

I sowed some Cobra bean seeds and some Romanesco courgettes, both from 2018.

I chitted some Cobra and nothing happened so I put the remainder in pots and put them in the propagator along with the Romanesco courgettes.

Nothing happened so I duly ordered new.  The morning after I open the propagator and guess what, all the Cobra beans and the courgettes are waving at me happily!  Should have waited.

I've found a heat mat to do wonders for germination, the vast majority of seeds germinate best between 25c and 30c. It just keeps them at a consistent warm temperature.

Once germinated moved them off though, otherwise everything gets really leggy

Mine were just cheap Chinese ones off eBay, they've lasted me about 5 years so far and I've used them to heat homebrew too, with a temperature controller

Something like this
https://www.amazon.co.uk/gp/aw/d/B07HL59XNH/ref=sspa_mw_detail_1?ie=UTF8&psc=1&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9kZXRhaWwp13NParams

So I bought some watercress seeds from Suttons early in the new year. They were sown in trays in a propagator set at 20C but after 4 weeks none had germinated (they usually take 3 or 4 days to germinate). Tried again with same result. Bought some Mr Fothergills water cress seeds and sowed them at the same time as some more Suttons seeds. Mr Fothergils seeds germinated 100% in 3 -4 days but the Suttons were a no show. So I decided to contact Suttons to let them know there was an issue with their seeds. Their response:-

We test all our seeds for quality and germination.
Your seeds will be replaced (not that I was bothered about that).

New seeds arrived and were sown at the same time as some of the first batch of seeds. New seeds germinated in 3 - 4 days but none from the original batch!

Do you really know how old seeds are and what condition they are in when you buy them? Hmmmm

I have seeds 5 years old that still germinate pretty good. Bit of a lottery but generally seeds from reputable suppliers are pretty good.

By the way watercress is worth growing. Just damp compost needed not running water.

Help chitting seeds?
Out of date or otherwise how and why?
Thanks cc