The most likely reason for poor insulin absorption, especially after enjoying good-quality and consistent absorption for years, is over-used sites. Even limiting infusion sites to three days still causes injury to the tissue. One of the factors that determines the extent of that injury is the amount of insulin that you infuse. Much less tissue damage occurs at 30 units per day than at 60 units per day.
If I were you, I would try to identify and experiment with some locations that you’ve never used before. This can really help. Once, when I just could not get good blood sugar performance from my abdomen, I switched to above my hips but around toward my back. I gave my abdomen a rest for about a year and even underwent a course of physical therapy to rehabilitate my abdominal tissue.
Changing up infusion sets is another great tactic to experiment with but I would not favor it over identifying a brand new location. Since you’re using a 6mm 90-degree soft cannula infusion set, experiment with shorter and longer 90-degree cannulas, angled sets, and steel cannulas. Again, I would not simply change infusion sets while using the same real estate. I currently use the Med-T angled Silhouette 13 mm cannula set.
This is a worthwhile exercise if you want to protect your long-term use of an insulin pump. Thanks for the reminder, I need to re-examine my infusion habits again. I’ve been pumping since 1987 and have some tired tissue, too. Good luck! Please report back if you find something that works.