I had the same thing happen to me a year ago. The investigator considered any reference under 2 years not valid toward the 5. I had a mix with one being 6 months and one being 10 years. My avg time known was prob around 3 years. I knew many people in the other counties, but being you are limited to the county I was limited.
However it's the judge not the investigator who makes the decision and mine was approved without a hearing. The judge makes the call, the investigator only a recommendation.
The problem is if you get denied (and you choose not to appeal it), you always have to put that on any application you fill out.