Seems time consuming if you;ve got access to the good quality cd recording.
Be mindful of some tape releases having extra tracks that sometimes take the play time to 85+ mins. Def. worthwhile in that case. However you wont get the full album on an audio cd. At least you'd have it on Mp3 though.
I think doing what you've considered to be a glorious waste of time. I look back, 10-12 years when i started ripping my tapes. I did EXACTLY what you're thinking of and I regret it. Because, all of em are easy to find as high quality rips now.
Depends on the release. In most cases, if you have a CD, don't bother ripping the tape. However, there are a few releases where the tape version is actually superior (sonically) to the CD. There can be numerous causes for this, as I've seen several over time. One cause is simply an error/lack of care when the master is prepared, or a manufacturing error. Tim Smooth's "Da Franchise Player" sounds better on cassette (to me) simply because a few of the tracks on the CD play at a slightly faster speed than on the cassette, which gives a different listening experience. Another example would be some of Cash Money's early CD releases were handled wrong and the CDs actually play at a much slower tempo than they should (sounds kinda like when you have a 48kHz song being played back at 44.1kHz).
The main issue you'll run into when converting from tape to CD (if you've got good equipment and know how to record it properly) is dithering, however a lot of people would argue that proper dithering to a cassette release changes the overall sound, because most people weren't listening to these tapes in premium cassette decks designed for every different type of cassette.
Tapes will sound different on different decks often due to things like Type I vs Type II (and vs Type IV in some cases, though type IV is typically a blank tape thing, from what I recall), tape material (chrome vs chrome plus vs cobalt etc), what type of heads the player has, wow & flutter, etc. It can get quite complicated. Ideally, you want to do a tape conversion with a nice Nakamichi (or similar) deck and record with professional equipment that will give you a 20-20,000 Hz frequency range with as little harmonic distortion as possible.
Then again, a lot of people are totally satisfied with a mediocre recording that was made with a cheap walkman going into the mic input on a laptop, so depending on how much of a stickler you are for quality, you may or may not care to make the best quality recording.