...Expect increases at 70 and 75, establish company loyalty, fly regularly, document training, and add an instrument rating if you can..."
Some comments:
Increases? Definitely, if you can even get a policy.
Company loyalty? Doesn't mean squat.
Flying regularly, training, additional ratings may help but when it comes right down to it, age is the biggest factor.
Don't think so? When I was getting insurance for my RV-10, 18 months ago, I wanted to have my Dad listed on the insurance. He was 78 at the time. I went through a well known broker and only two companies would write the policy. The cheaper one was in excess of $6000 a year; the other one was over $10,000.
Dad has been flying since 1957, has over 40,000 hours, all the ratings you can think of, and is an active instructor logging 50+ hours a month in Piper Cubs. Yes, he is also a Wright Brothers Award recipient.
I also wanted to list my 22 year old son, who has 500 hours. That was no issue, and only raised my premium by about $900 a year.
In the end, I opted to not list Dad...he flies the aircraft under the open pilot warranty, 500TT and 25 in type.
Point is, AGE is by far the biggest factor; loyalty, activity, and experience seem to be a very distant second.