My question is aimed at understanding the how much Delta-V is needed for orbital maintenance in different orbits. Obviously, there still is some residual air resistance that decreases as the orbital altitude increases. How should the delta-V needed for station-keeping and orbital maintenance be estimated? Is there a formula that is often used or a rule of thumb?
Good question, I’m also interested if someone has a more specific answer to share!
On the following table, you can find the required delta-v per year for different orbits.
And about formula, I'm not sure but maybe this page can give you an idea: https://en.wikipedia.org/wiki/Delta-v