I waited more than 20 years after hiring in to buy my time and it cost me about double the price that I would have paid had I started paying when I was first hired. You cannot buyback your military time after you retire. And it takes some time so you should not wait until you’re ready to retire. I strongly recommend you take the plunge and start the process ASAP/NOW. There’s no interest charged if your time is bought when you’re new to the Postal service. There is a 2 year grace time before interest begins accruing. The good news is even after waiting 20 years my total was only about $3600. The better news is you can use a payment plan that you design to pay it off. You can pay one lump sum, or utilize payroll deduction for as low as $25 per check. I did $50 per check. I was finished paying in less than three years. You choose the payment