How long is too long

Back in 11/06 my daughter was at the doctors. The next statement I received said that the amount for the services performed was pending insurance. Since then I have had many other services from the same doctor, and on each monthly statement I get is kept saying pending insurance. I paid everything off of the current balance 4 months ago, and have not received any statements. All of a sudden I get a statement in the main today stating that if I don't pay for the services back on 11/06 that they are going to send it to a collection agency. My question is, how long does a doctor, company, etc have to collect their money? Too me, if they don't collect with in a year, I should never have to pay it. Do I have any legal standing for not paying them? Any help would be greatly appreciated.

[annjd]

See debts and judgments: http://www.worldlawdirect.com/article.php?id=1758

See above for the technical legal date.

But often if the delay is serious and they are responsible they will settle for a partial amount. You can argue it is just unfair and burdensome to be billed so late.