my opinion is this - if it is an LPA for personal welfare then it should be registered when it is done - healthcare decisions often cant wait the amount of time it takes to register it with the court of protection
However, the personal finance one in my opinion could wait - it can take months to get it registered, but you can usually hold off creditors and bank accounts/nursing homes etc by telling them its being registered, or use interim measures. As it costs 150 to register it, in my mind its wasted if it's not needed to be used. Also, things change, and if for example you had a falling out with the attourney before they needed to use it, but it was activated, you could be in a potentially vulnerable position, and have to pay more to re-register with new details