“Am I thinking about it correctly?”
Vinnie,
A lower-tier, BBB2/BBB- issue, due in '59 and not eligible for the 15% tax-rate, that can be estimated to lose money over the long haul due to the impact of inflation isn’t “an investment”. It’s just a bad idea.
Give me time to find the spreadsheet I built for bonds years ago, and I’ll run the numbers, plus offer some explanations that get into things like the diff between agency-assigned ratings versus market-implied ratings and how to estimate whether a bond is priced fairly or not.
Yes, bonds can have a role to play in retirement portfolios, and even a big role. It all depends --as always-- on one’s means, needs, interests, skills, goals, and opportunities. There is no "one size fits all " and the various allocations offered by financial planners along with assumptions about “safe withdrawal rates” are nonsense that works well in backtests but not out of sample, going forward.
Suggestion. If you want to break into the bond game, you should do some reading, and I’ll make the same suggestions I made in another post which you can find here.