In 1990 I bought the best audio equipment I could afford. It is much better than I had ever had before. I have had it ever since. I enjoy it.
Now, 33 years later, some of the equipment has started to fail. I am almost done sending stuff out to have it refurbished and in some cases even upgraded. It sounds better than ever. I see no need to replace anything with things that won’t last nearly as long.
Now seeing that I'm a human being, I still look for little ways to get a little better sound. Thanks to the advice from some of the good folks on this site, I have replaced my cheap stock interconnects with Audioquest Tower cords. I noticed improvement right away and it seems to get better every time I turn the system on. Burn in? Perhaps. Maybe I’m just enjoying it more, who knows? My next step was to order the SP6 speaker cables from Morrow Audio. They are currently undergoing the 20 day burn in process at Morrow. Once I have those and am used to them, I’ll look into room treatments. That will about do it for me,
An investment? Well, only in the manner that I will have had decades worth of musical enjoyment for myself at a reasonable cost that I can afford. That’s a "sound" investment if I do say so myself.
EDIT: I should mention I purchased the Morrow Audio speaker cables when I received their Black Friday Sale notification from Audiogon.