If no one has guessed yet, I consider myself a very conservative investor. So I too left my stable value fund alone (in my 401(k) from Megacorp). It only gets about 2% as others have mentioned. So, I'm leaving money on the table, most years. But, during the great recession, my SVF was one of the reasons I didn't lose any net worth (other reasons were my small commitment to precious metals and some other "cash like" products which continued to earn 4+%.) No brag, just fact. SO, since the recession turned around, I've not gained like many of the folks here who were "all in" on stocks. Of course, I didn't have any losses to "come back from" either. I only have about 30% in stocks right now. With my "guaranteed" sources of income (modest pension, very nice SS check(s)) plus my conservative portfolio, I seem to be good to go to age 100 unless inflation rears its ugly rear.
I don't recommend this particular approach to investing, but it seems to work for me. I saved more than I needed, so why take too many chances going forward since I seem to have enough to more than meet my life-style needs. As always, YMMV.