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.
You can roll your 401(k) money into the Thrift Savings Plan, which may be a good idea because it has incredibly low fees (18 cents to 19 cents a year for every $1,000 invested for most of the funds, which equals just $18 or $19 a year in investment-management fees on a $100,000 portfolio).