[Yorkie]

If you have stuff in your shed that has been there ages - it's always best to check on-line before you use it.

What time scale would you recommend checking online with these chemicals MOS ?
Every day or every month ? and where should we check online for this information ? Do I need to check every time I use a product before it's printed use by date ?
Are you talking about the product degrading over time, or are you talking about retrospective health concerns ?

In addition to the RHS website previously mentioned, the Garden database is the online definitive answer.
https://secure.pesticides.gov.uk/garden/prodsearch.asp

You need to click 'Get Results' at the bottom to start the search once you've input the relevant details, not just hit the Enter key 

The MAPP number will be the most reliable way to check your particular product.

[pink aubergine]

Sorry , by banned chemicals, I meant chemicals that should say be used only on flowers but not on veg, so certainly not meant to be ingested . So banned for edibles.
 Thanks for all your threads, glad to see there are others out there concerned about what we are eating !

[seaside]

People are as confused as ever, and one has to ask just who is responsible for that confusion. The industry needs to take a long hard look at itself, but I doubt it will. The bottom line is still to sell as many items as possible. Marketing people are worse than politicians these days, and there's still the science that still can't agree.
I know what I do. If there is any doubt whatsoever, I won't use it. Which means it's soap solutions, home made efforts like garlic, or nothing. Well, I say nothing, but that's not true. The organic approach is effective enough to get a good crop, it just takes time and a little more effort. Cover if absolutely necessary during the most vulnerable time, plant out only strong seedlings, and attracting beneficials DOES work over time. Sometimes even a good hard spray of plain simple water gets rid of much of the problem.
Knowing what to look for and prompt action is often effective. Regular tilling/disturbance of the soil is also very helpful to many pest problems. And remembering what parts of the plot seem more prone to problems, and then planting accordingly, is surprisingly effective.

[Madame Cholet]

I found covering all my brassicas with fine net curtains worked, and waiting till the plants are bigger before planting them out helps too.