I had one a few years ago. I believe I kept 100% off of it for about 8 weeks with some PT and began a regular running regimen 12 weeks afterwards. I would plan on not running for at least 3 more weeks and get cleared by your doc.

---

Strava

Need some more information before commenting:
1. When was the stress fracture diagnosed?
2. How was it diagnosed?
3. What is the location of the stress fracture?
4. What has been the management to date?
5. What are you able to do at the moment?
6. What base had you built before the injury was diagnosed?

I was diagnosed 6 weeks ago by mri, fracture is on left tibia, have been low impact using elliptical, pool running and cycling with no pain. I had run a marathon 6 weeks ago and two ultras before that so I had a large base already built up. Also have been in a boot on days when I am on my feet a lot at work.

It sounds like you are doing all the right things. I hate to say it but the recovery from this can be very slow. I have had a few tibial stress injuries and one stress fracture and generally it has been at least 3 months before I can return to anything reasonable load wise (longer for my stress fracture). Water running is an ideal backup if you can tolerate it (I cannot....).
I was in a boot for 6 weeks with the stress fracture for any loading (ie walking etc and all work, just not around the house). Was a PITA but what I needed.
Also have to remember that once you decrease the loading through any bone through loss of impact forces, your bone remodelling will be such that it can be inherently weaker and increase your risk of re-injury and new fractures if you get back into things too rapidly.
15 weeks sounds potentially optimistic but I would imagine you probably have at least another 6 weeks of minimal loading ahead of you, then probably 4-6 weeks of gradual build, which means you may only have 3-4 weeks of being able to load fully prior to tapering etc.

Twin Labs makes a "Bone support" supplement - look into that - or at least they did years ago. It's mostly calcium; calcium is crucial for bone healing. I don't know what other magic is in it but that stuff helped me recover from the string of fractures I had in college.

---

maybe she's born with it, maybe it's chlorine
If you're injured and need some sympathy, PM me and I'm very happy to write back.
disclaimer: PhD not MD

Dont rush things. There are so many things that can go wrong and make it a lot lot worse if you start running again without it fully healed. Trust me Iv been there.