I learned my lesson when I was still pretty young and very poor.
I discovered the rock group Manfred Mann when I was a senior in high school. I was aware of their singles and wasn't interested. Then I heard an album and was hooked. Over time I bought everything by three groups Manfred was in.
About 1971 he started a new band, his fourth. I bought three albums by them, going into maybe '73 or '74. I never liked the fourth band, called the Earth Band, but I kept buying the records because I was a completist.
At that point I finally realized that the party was over and regained control of my spending. Since then I have bought everything available by some Canterbury groups up to a point when their productivity ground to a halt and only tapes from the vault were being issued, but I have never again been a completist.
So I agree with the above statement regarding diminishing marginal returns. When it stops being fun, count me out!