Yes, duty of disclosure arises as soon as any change occurs.
I don't think that's necessarily the case. As with any insurance policy contract, there is an absolute good faith requirement for full disclosure when entering into the contract. But once the contract comes into existence, the insurer has taken on liability for insurable events for the 12 months duration of the contract, based on their assessment of a
full and fair disclosure of the facts as they existed at the time of entering into the contract - including an assessment of the risk that those facts might change over the period of insurance.
Of course, if there's a term in the contract
requiring subsequent disclosure, and there often is for health issues, that's a different matter. But, absent such a term, I don't see how a disclosure requirement arises.
What I was saying above is that duty extends to any of the details that were provided when getting a quote.
Again it depends. If you want to change the basis of the contract, eg a different model vehicle, additional drivers, different category of use, etc, you must notify this or you won't be covered for the changes.
To take a possible analogy. If you insure your life, it's based on your health status at the time you take out the policy. You don't have to notify the insurance company if you subsequently suffer a serious illness, while the policy is in effect. But you do if you change the basis of what you're contracting for, eg if you declare yourself a non-smoker and subsequently take up the habit. Or, arguably, if you take up employment as, say, a bomb disposal officer.
Or, if you insure your house, and Ireland's most prolific burglar is released from Mountjoy and promptly goes on a one man crime spree all along your street, that's a very relevant consideration, but you've no duty to disclose it during the currency of the policy. Similarly, if your road floods unexpectedly for the first time in living memory, and the expert advice says it's likely to do so again, you would need to disclose that
at renewal only and not during the currency of the policy.