However, don't bonds go up when interest rates go down?
Yeah, but you also get higher interest payments. The worst-case scenario for bonds is very, very, very mild. The medium-bad case for stocks is about 10 times worse than the worst-case scenario for bonds. It's silly to buy stocks instead of bonds if you're worried about risk. No matter what state the bond market is in, it's always far, far, far, far, far, far less risky than stocks.
And since interest rates really can't get much lower, if I purchase bonds now aren't I literally buying at their lowest point?
No. But if you're really worried about it, stick to low-duration bonds. A short-term bond fund will lose practically nothing even if interest rates rise dramatically. An intermediate-term bond fund would lose relatively little in such a scenario and the break-even point would be far sooner than you'd think. For long-term investors, these fluctuations are inconsequential. And even if they weren't, what would you invest in instead? Stocks? They're a billion times riskier than bonds.
Would it make sense to buy them later in life when I'm trying to preserve more of my wealth?
Yes, but that says nothing about whether or not it makes sense to buy them now.
If bonds only go up when interest rates go down, and interest rates are currently at the lowest they can get, wouldn't it make sense to buy bonds when interest rates are higher? Appreciate the education on this topic.
Market timing doesn't work.