I’m not the person to answer you about holding gains after stopping Reclast, sorry. But I’m interested in the same info. I’ve done 2 Reclast injections, heading for the third in a couple of months. I’ve only had the 2-3 day type side effects, though.
I see the endocrinologist next month, I’ll ask about how long Reclast should affect bone after stopping as that’s where I’ll now find myself. Originally I was so caught up in breast cancer treatment questions that Reclast was just another drug that I took. Preventing compression fractures is my number one concern as I age.

Here’s a recent study, seems like good data about Reclast, but one of the 5 authors does have a connection to Novartis. This study shows that when talking bone strength there is a difference between simply improving density and preventing fractures.

“We found that a single dose of 5 mg zoledronate prevented bone loss for 9 to 10 years in the axial skeleton and reduced the level of a bone resorption marker by at least 25% for 8 years.”

But that is about preserving bone density. Preventing fractures is something else. From the same study . . .

“Current analyses suggest that a single 5 mg dose of zoledronate and 5-yearly doses of 2.5 mg zoledronate would reduce the incidence of each fracture type over 10 years.”

Side effects from Reclast do seem to be dose dependent. Hopefully a lower dose might be easier on your body.
https://onlinelibrary.wiley.com/doi/full/10.1002/jbmr.4453