A biller I hired about 3 years ago convinced me to try a new tack on this. Since we are a Peds practice, she figures 'the kids will get sick for sure at some point and they are going to need us'.
So, we don't turn anyone to collections for about 18 mo, no matter what they owe. The rationale is: if you send them to collections, you collect cents on the dollar anyway- if that. Versus, if they want to be seen, they have to pay at least part of their balance and we roll on from there.
After 18 mo of no response, we do turn them over to collections. (previous limit with us was 3 mo of no response).