Getting close to retirement now, and am watching a lot of advice videos suggesting some split between stocks and bonds where the ratios vary with age. I'm not sure the TSP really has good "bond" options. I find the F fund really frustrating, in that what looks like a good day for bonds at 4 PM can change after 4 PM to a lesser increase (or even a loss). And G fund isn't even close to beating inflation. It would be better to have more bond options in TSP so your really could do a 60/40 or 50/50 split with stocks, but I guess to effectively get that you have to leave the TSP (which I'm loathe to do)....I'm considering keeping the stock portion of my portfolio in the C/S funds, and then move the bond portion out to Vanguard.
I had a friend retire who told me he kept his TSP open just to have access to the G fund. He has fond memories of big returns in G - I don't think we'll see that again in the near future anyway....