Can I keep going back on Recast

I have been on Recast for 3 years and have been of off it for 2 years, doctor has recommended Forteo for 2 years, after that I don’t know? I don’t know if I can go back on Recast, can’t do the oral meds. Maybe for 2 or 3 years, what then, I’ve heard that 6 years is the limit for Recast, or can you stay on it for many years and keep doing holidays