The time any mis-declaration will matter is if you ever end up with a significant claim. The one time you will really want your insurance.
Minor things they are unlikely to care, although obvious "errors" may be detected.
It basically boils down to whether they are convinced you materially lied on application. If they are, then they may void your insurance. Or they may pro rata it.
Your only option then is an appeal to the ombudsman who will look at the same data and decide if the insurance co are being fair or not.
Its really not worth ever misdeclaring. There are enough players in the UK market to make it highly unlikely that someone will not have you as a target customer.
The DVLA time limit for points and spent convictions is irrelevant in regards what an insurance company decides it wants to know in regards deciding what amount it would require you to pay in order to cover you.
The policies are written in good faith, they expect you and its implied you will, act in good faith by answering truthfully the questions they ask.
If they can prove you acted in bad faith then its likely the ombudsman may support them in voiding. Under these circumstances they will still deal with 3rd party, but they will likely come after you through the courts to put them back into the position they would have been had you not lied.