Recording Degradation on Recording to reel to reel

Another thing to keep in mind is that those early 7" pre-recorded tapes were sooo close to the master, that I’m not sure one can get the same reproduction today, even with today’s one steps, and other pressings (SACD and 192 kHz files included). It’s one of the main reasons why they are so coveted even today. Granted, the S/N can’t approach today’s technology (and S/N is a definite priority with me), but the dynamics (on the right playback equipment) on some of these tapes is just mind-blowing. I only own 7 of them at the moment, but whenever I throw one on, and put on the headphones, I’m still to this day blown away by their dynamics, to the point I feel like I’m almost sitting at the mixing board. Don’t forget to keep those tape heads and capstans clean.

Pre recorded  tapes were duped at higher speeds.  Irrelevant to the question. In 40 years of intensive tape recording I could immediately tell if the best available tapes had ever been previously recorded upon. Cheap tapes were so bad to begin with it didn't matter.

Keep you heads, tape guides and capstan clean.

De magnetize heads and metal parts on tape path after some playing hours and keep the tapes stored properly.

Somewhere i have read that tapes can last 50 years, i think this claim is rather conservative.

To your question that would depend on many things, like tape quality, speed, tape machine, weather conditions...

Cheap tapes were so bad to begin with it didn’t matter.

...not to mention that when recording using analog tape; for maximum audio quality, the deck’s equalization and bias must be set up for the particular tape formulation being used to record on. With calibration tapes, that used to be fairly easy to do, and common practice with professional decks (and probably still is if you own one), but most consumer decks were probably set up using only one formulation, and hopefully that would generally provide halfway decent performance for all tapes used when recording. Not that it’s a big deal anymore, since I never record (onto) cassettes anymore, but my Denon DN-790R cassette deck actually allows me to listen to the audio being recorded on the tape, and adjust the bias while monitoring the audio of the tape, while switching back and forth to the audio on the tape vs the input audio. Almost all professional reel to reel decks allowed this too, along with high performance consumer models.