[TOPIC] Diabetes

Most people don't die of diabetes, they die of complications from a compromised immune system.
If he "develops" Diabetes, it's most likely Type 2, and with proper diet, he'll live as long as anyone else, and never need insulin.
If he does manage to have his pancreas shut down, again, with a low carb diet, he'll never need to worry.
If he continues to eat as before, a high carb or high protein diet without enough fat, his body will make sugar- and one of two things can happen. He can eat too many sugars, and go into a high blood sugar comma (actually fairly hard to do, but if he binges on candy bars, he could conceivably kill himself) or eat too little, or too much time between feedings, and have a low blood sugar problem. He'd have to be around people who don't know what to do, or by himself for low blood sugar to be a real problem, but if he's alone and passes out, his brain could shut down and he could die in a matter of minutes.
My Dad's a Type 2 diabetic, and we had a Type 1 diabetic dog. She did get insulin shots, but we could have switched her over to a high fat, high protein, complex carb (broccoli, beans, etc) and she would have done alright- except she had joint issues and getting fat wasn't an option.
They have both had low blood sugar (hypoglycemic) bouts where they have seizures or faint or slip into a comma- both responded to corn syrup or sugar (Jolly Ranchers for Dad) put in their mouths and absorbed through the membranes of the mouth.
If you're thinking of diabetic ulcers and such- those can be all but impossible to cure, but they can take years to kill someone.

I would say, 15 years maybe?
At that age, it would be Type 2 diabetes, which has often been called the "silent killer". People can be years between the time the diabetes appear and the time they are diagnosed. The body gradually "adjusts" to higher and higher level of blood glucose, and the person might not feel any symptoms for 10+ years.
Type 2 is usually first treated through diet and exercise. Then, a variety of oral medications are usually given to help things out, because in many/most cases, patients find it hard to change life-long habits in their diet. When the diabetes becomes unmanagable through pills, patients are put on insulin, but their body still produces *some* insulin, so even if it was not available, they would not die as fast as a person with Type 1 (in their case, the insulin production is null and they would die within a few years from diabetes, like it used to be before insulin was discovered).
What really brings up the death rate in elderly diabetes patients is the complications : cardio-vascular problems (heart attacks, strokes), renal problems (renal failure), infections that will not heal leading to amputation, in most cases of a foot/leg.
(My boyfriend was diagnosed as a Type 1 a few years ago and we followed all the information classes together, which were sadly mostly intended for Type 2 diabetes patients)