1. Ask an Expert: How long? -- Netwellness Homepage
We base this in part on how far the complications of diabetes may have progressed at the time that a diagnosis is made, and also on our understanding of how sick a person can be for long periods with the condition going undetected.
http://netwellness.org/question.cfm/41869.htm

2. References Chapter 9 -- University Of Colorado Health Sciences...
A prospective study of the development of diabetes in relatives of patients with insulin-dependent diabetes. Insulin antibodies in insulin-dependent diabetics before insulin treatment. The world of insulin-dependent diabetes mellitus:
http://www.uchsc.edu/misc/diabetes/oxref9.html

3. Arch Intern Med -- The Effects of Improved Glycemic Control on Complications in Type 2 Diabetes, ...
Exogenous insulin administration and cardiovascular risk in non insulin-dependent and insulin-dependent diabetes mellitus. The effect of intensive treatment of diabetes on the development and progression of long-term complications in...
http://archinte.ama-assn.org/cgi/content/full/158/2/134