1. I think a back-standing option would probably be best for long periods of time, especially in high heels.
2. As long as you get a doll with standing bolts on her feet, you should be able to store her standing indefinitely. My dolls usually have shoes on and are stored standing but I don’t have any experience with high heels so I’m not sure about that part.
Another thing to keep in mind is the doll will need a third point of contact to remain standing. For example, you could have her leaning slightly against a wall with her butt and/or upper back touching the wall. In that case, you may want to have a layer of memory foam between the doll and the wall to prevent deformation over time.
Some doll brands such as WM, YL, SE and etc. have stands designed for storage and display purposes.
3. From what I have read/seen, the manufacturers recommend you do not store the dolls in high heels. For storage in a standing position, you need all three points of contact on both feet to be even with the floor. With the diagrams I have seen, it looks to be as if gravity would take over as if she is standing on a hill and her feet would proceed to slide downward over time. Thus damaging her feet. And as was stated, always lean her against something padded with either memory foam or a rolled-up towel.
4. There is no good balance with high heels. There are no toe bones, so you have zero support at the bottom tip.
I keep my dolls standing on walls for years, but flat foot.
