wrote:

This suggests that a few years ago the payback in reduced insurance premiums
was around 4 years. In the current insurance situation, it is therefore
quite believable that payback could be quicker.

What current situation? The insurance on my 182 keeps getting cheaper.
I called my broker and asked him what the difference was between an
instrument and non instrument rated pilot with my 900 hours in my plane.
No difference. Not only did the premium go down $170 this year, I
changed from USAIG to Global, they rasied the hull value from $65K to
$70K without me asking them to do it. My insurance has gone down in
each of the six years I have insured it for. If this insurance
situation gets much worse I may have to buy another plane.