INDEF to Voluntary Separation?

Indef was still at the pleasure of the service keeping you on duty. Federal Time in service on active duty is what counts toward your active duty retirement. After you get out it's another type of calculation. Hope that helped some but I'm sure others know more!

For the separation part, you can request separation at any time. Indef is meant to allow NCOs to manage their career similar to officers. You will have to serve any obligations you currently have like SRR for PCS, promotion or GI Bill transfer. Then you'll request an ETS date from separations. It's in AR 635-200

It's pretty simple. In itself, AD time only counts for TIS for leave purposes. So instead of 4 hours every two weeks, you'll hit the 6 and 8 hour mark earlier. IF you want the time to count for Civil Service retirement, then you must buy the time credit. As I recall, I had to pay 3% of my calculated base pay. Worked out OK as I had 10 years AD. Back when the pay was much lower, I had to pay $10 Grand to get 10 years. The first two years of payments were interest free and the last were at the Treasury Rate. Payroll deduction worked well. Bottom line, even under FERS, the difference between a 32 vs 42 year retirement made it a no brainer choice. Just remember the CS annuity is much less than the old FERS level. Make sure you do at least 5% (I did 10%) in the TSP as 100% earnings on the first 5% every payday is a slam dunk.