Ozy was diagnosed with only iaa (68% high Dec 17, 2013 ss) and his IGF-1 (acromegaly) was negative but high on the negative end. I want to say it was in the 80's. Here is his
spreadsheet link. Donaleen switched him from Lantus to Levemir Dec 21, 2013 and was really, really happy with the Lev. Most people now switch high dose cats to Levemir because of its long duration and neutral ph.
One tell-tale "look" of a spreadsheet of iaa cats - often when the dose is increased, they might have an initial response and their BG might drop into a lower range, but shortly after that it will appear that the dose has stopped working and the blood sugar range rises. Wendy coined the term "going stale" to describe that response, and that's a perfect description of it.
Acro spreadsheets, on the other hand, can sometimes stay at a dose for a long-ish period of time. The tumor that causes acromegaly is called "pulsative" meaning that it can ramp up or down in its hormonal secretions. Or the dose can go up and go down. Some acro cats can go into remission when the tumor takes a break, then end up back on insulin again in a while. But you don't necessarily see that pattern that the dose initially works, then stops working. By the way, as others have said, I really don't think you can rule out acromegaly without a test. It is more common than iaa - the latest study shows 1 in 4 diabetic cats have acromegaly.
R is "regular" insulin, either Humulin Regular or Novolin Regular. You can buy it in the US without prescription, just ask at the pharmacy. It can be a great tool when it is needed. Most people with high dose cats choose to use it, but there are people with non-high dose cats that also use it. One has to be careful with it because it has a nadir, just like Lantus or Lev, and you don't want the nadirs of both insulins to occur at the same time. Timing is everything with R. If you are interested in it, let us know and an experienced R user would guide you. In cats with iaa, the action of R can be extended, so it isn't as quickly in and out as it is in non-iaa cats.
I don't see any advantage in holding the dose longer in any diabetic cat if it's not getting the cat into normal numbers. Holding onto a dose that isn't working causes
Glucose Toxicity to develop and the result of that is having to go up in dose.
High dose kitties have higher/lower IAA percentages and higher/lower IGF-1 results. The result of this is the perhaps more than any cat, the phrase "know thy cat" is critical.
If you decide to test Mocha, I'd definitely test for both acro and iaa. Cushing's is the 3rd cause of insulin resistance, but it typically includes fragile skin symptoms and I would say is the least seen here. The acro/iaa are relatively common. We usually suggest people get their cat tested if they get to 6u per shot.
By the way, if you're following the guidelines laid out on the Tilly page, you would be increasing the dose a little faster. You can increase in 2-3days when a cat is all in high numbers. As much as you test, and with Mocha having passed 6u, I wouldn't hold on to a dose longer than those 2-3 days until you are seeing green numbers. But of course, it's up to you.
She clearly gained respect for my unorthodox (in her eyes) treatment and it was smooth sailing. When he went OTJ she said "he is amazing". 
).