Been faithfully married 30 years, retired and was having sex pretty much daily (except during fights) for quite awhile... Then had a major misunderstanding with wife two months ago and now we have been having sex twice or more a day since, with no indication that it is a passing phase... I'm pretty sure she is doing it for me, as opposed to her needs, which I'm sure are much less, but not sure if it's a problem, or if this is the new normal and sustainable.

Very common cause due to erectile dysfunction as you go to certain level age as hormones changes, but it is curable take a proper doctor advice and he/she can guide you well / can treat you well on this conditions.

The best way to prevent erectile dysfunction is to make healthy lifestyle choices and to manage any existing health conditions. For example:

Work with your doctor to manage diabetes, heart disease or other chronic health conditions.
See your doctor for regular checkups and medical screening tests.
Stop smoking, limit or avoid alcohol, and don't use illegal drugs.
Exercise regularly.
Take steps to reduce stress.
Get help for anxiety, depression or other mental health concerns.