Here's an approximate timelime for complications that can be expected from poorly controlled diabetes. While cardiovascular complications are very important, it is usually not the first thing I worry about. So I would not expect cardiovascular symptoms early in the disease course. OTOH, early insulin use may have some benefit in preventing some of the other complications - but this article makes no mention as that was not the focus of their study.

http://virtuallabs.stanford.edu/diabetes/Timeline.pdf

These timelines depict the rough progression of complications in poorly controlled type 1 and type 2 diabetes mellitus. Also indicated are the time points at which screening for certain complications is recommended.
Type 1
Diagnosis: Organs highlighted – Kidneys, Pancreas
- Polyuria/polydipsia can signal diabetes onset
- Diabetic ketoacidosis may be the presenting feature of diabetes

5 years: Organs highlighted – Eyes, Nerves, Peripheral Vascular (Arteries), Kidneys
- Microalbuminuria begins
- Annual foot exams, eye (including retinal) exams, and urine screening exams should
begin

10 years: Organs highlighted – Eyes, Kidneys
- 60% of people with poorly controlled diabetes have retinopathy at this point
- Overt nephropathy may be present

15 years: Organs highlighted – Eyes, Cardiovascular
- Blindness resulting from diabetic retinopathy may occur
- Cardiovascular complications become symptomatic

20 years: Organs highlighted - Kidneys
- End-stage renal disease may occur after years of nephropathy

Anytime: Organs highlighted – Pancreas
- Diabetic ketoacidosis may occur, especially with infection or non-compliance with
insulin regimen

Life Expectancy: Organs highlighted – n/a
- Due to the complications of the disorder, life expectancy is 7 to 10 years shorter for
people with poorly controlled diabetes than for people without it.