A guide for people making the decision for the first time.
Most people meet this once and never think about it again, which is exactly why it is worth reading up on.
Where to go from here
The exceptions matter more than the rule, and there are three of them. The figures move about, but the direction has been the same for three years.
The exceptions
Nobody is required to explain this to you, which is half the problem. There is a deadline involved, and missing it costs more than the difference.
None of this is urgent, but it is worth an hour before the next renewal.