Space Force mulls 8-year active duty enlistments for new recruits

This implies that, upon the second re-enlistment, an Enlisted Member will be able to complete a 20-year career (with four years over, so 24 years). Each service adjusts their service policies in order to best support their staffing requirements. If eight-year hitches do this for the Space Force then members should use this policy to build their careers.

They do. New military members now have the blended retirement system, which has a TSP along with the high-36 for 2%/year after they serve 20 years (effectively 40% starting at 20 years). If they leave at 8, they still retain the TSP, which the military automatically starts at 1% but members can put more into it with up to 4% matching from the military.

If you can do 8, 10 is a chip shot -- If you can do 10, then you're halfway to retirement. 8 years is a long commitment for young men and women to make