How often would you actually be in space?

Is centripetal gravity acceptable for long periods of time? Yup. Apart from any motion sickness, centripetal gravity is just an acceleration, same as gravity is; so the biomedical effects are identical.

-Ian "If you want to build a ship, don't drum up the workers to gather wood, divide the work, and give orders. Instead, teach them to yearn for the vast and endless sea." -Antoine de Saint-Exupery