Makes me wonder if 170 days was a typo. Its an odd number to choose, where 120 is more common. Regardless, it will stay on your credit report for 7 years, but generally as long as it is paid eventually, the effect on your credit score drops dramatically after 2 years. It would still be a good idea to get this resolved amicably to keep your pristine credit. Perhaps get a personal loan or HELOC or some other loan to consolidate all the bills, pay them off, and then work on paying off the loan.
Also, its not unusual for medical billing to get screwed up, since it usually goes through a 3rd party provider who then bills insurance before billing you with the balance. Lots of people invovled with lots of opportunities to screw it up. I once worked for a major health insurance company, so I know how complicated the stuff gets and how often there are disputes about who is responsible for what.