@slaws55 for certain patients, Forteo can be taken longer now.

Online:

The new recommended treatment duration section of the drug label states that the use of Forteo for more than 2 years during a patient’s lifetime should only be considered if a patient remains at or has returned to having a high risk for fracture.

slaws55, there was a worry that these medications could cause cancer of the bone because it seemed to cause cancer in the rats used for original studies. A genetic cause for cancer in the rats is now blamed and aftermarket studies have disabused us of the the association.
A different issue could make continued use unwise. This class of medication works by increasing the process of clearing fissured bone and replacing it with new bone by increasing the cells that repair. Those cells stimulate production of the cells that clear damaged bone. It is thought that at 18 months the balance between the cells shifts to an imbalance toward breaking down the old bone. We can chart the balance with the use of bone markers. But we don't know the perfect balance.
It is clear that in the early burst of osteoclasts with Forteo or Tymlos humans build strong, integrated bone.
I am finding more specialists who are prescribing a third year. The prescribing physician I see has prescribed a third year of Forteo. My frax risk is 12 and 13 %.
If you have been off Forteo for a while, two more years would be a good option for you.
CTX drops rapidly after a month away from the medication.
I've heard of patients prescribed four successive years.
I hope to be on it till eternity with brief interludes.