Same experience, both with purchased tapes (e.g., IxExSpue, If) as well a my old mix tapes. SQ of newly purchased tapes (music only available on tape: E.g., Rue Oberkampf "Green Eyes"), and my old tapes is comparable. All the naysaying re old tapes being nothing but e-waste, sorry, not my experience at all. Lots of fun going down memory lane :-)
Who said tape doesnt last :^)
So I am kicking back listening to The Canadian Brass on cassette (DONT JUDGE ME) when I started wondering if these fine musicians were still performing (they are). When I looked at the discography, I saw my tape ("Champions" by Canadian Brass) was released in 1983. 1983! It still sounds rock solid on my Nak deck! For grins and giggles (and because I am nursing bruised ribs) I played some other tapes dating back to 1975/1977). These are tapes that are pushing 50 yrs of age! The fact they still sound good is a testament to the quality of construction, materials, and the care I use in storage.
It just boggles my mind that I have had some material that is still playing. Of course, having opened my mouth, the next tape I play will break and spool out inside the cassette well.