If you’re not seeing anything of concern in the SMART info then there’s little to worry about. You could install/run smartctl from the command line, or for something with a gui try gsmartcontrol / any other app that can interact with your hard drive diagnostics.
Hard drives can last a long time, as a general rule if your hard drive made it through its first 1-2 years without issue then there’s a good chance it’ll keep chugging along for years. I personally haven’t found that hard drives consistently die in 5-7 years, not too sure where you got that info from.
In any case backups are your friend, not just in case the hard drive dies but there’s always the possibility that your entire OS blows up somehow or you get a bad case of malware.
Investors that factor in world markets would probably do okay as long as you’re talking just U.S. economic troubles. e.g. right now VT (total world stock ETF) is weighted 64.70% U.S. market due to market strength. So in theory if the U.S. tanked and other countries have better markets for investing then the weights would shift to the other side and maybe being closer to 30% U.S. vs rest of the world’s markets weighted towards 70%.