I am not sure if this addresses your question exactly but it is my understanding that : Postmenopausal women experience a shift in bone remodeling, with bone removal (resorption) outpacing bone building (formation) due to the significant drop in estrogen levels following menopause. So after you stop the Evenity your bones are not forming bone as usual before menopause (the bones are experiencing removal of bone) so I think that is why you need another drug to lock in the gains (or prevent his breaking down).

I have read different things on the internet about protection against vertebral fractures. It appears it does protect somewhat but has to be followed up with other drugs.

I would say that whether the drug is worth the risk of side effects would depend on your particular situation. For me it was as I felt it was the best treatment for me right now. I have taken 2 injections without any side effects, age 71, T score was -3.7. I am still considering what I will use after I finish the 12 month course of Evenity.