Age-. The general rule in the industry is that once an A/C unit reaches 10-15 years, the idea of replacing the unit is usually a much better investment than putting money into an older system. If your system is at this threshold, it's usually wise to begin expecting, not wondering, when the system will fail.
You can keep the money in the TSP after you leave your federal job to benefit from the low fees, or you can roll over the money into an IRA or a new employer's 401(k), 403(b) or 457.
For example, if you want to borrow $10,000 from your TSP, you will receive a check for $9,950. The interest rate you will pay for the life of the loan will be the same as the rate paid by the G-Fund, which is the government debt option in the thrift savings plan.