I think im quite loyal(until my loyalty runs out-which I hv different thresholds for):
40(or 30 plus yrs): Suzanne Vega, until she was no longer a major label artist n I lost touch with her new(-er); I bought her best of compilation CD set tho I had most(all?) but on cassette/CD.
30(or 20 plus yrs): Tori Amos, similar to above
5-10 yrs: R.E.M. sometime in the 90s till Monster album or next one-i nvr bought pre-Monster albums as I nvr could get em on cassette/CD cost too ex(or distribution in S.E.A just too scattered then) or I only liked the songs on MTV/great MVs. After they got big n Bill Berry was ill n left, or even before tat their music or albums were out if my reach, both mentally n maybe physically(as in I dint search for the albums anymore). Then they disbanded.
Rachael Yamagata n Vienna Teng iv lost ground(I think their on hiatus tho) but I bought all their earliest CDs I could.
Books: if I'd been alive in the 50s, (n was aware of their work) I'd hv bought Asimov's n Heinlein's fiction until 80s/90s when thy stopped(died).
Douglas Adams I bought his books in the early/mid 80s until he stopped(died). Then a new Hitchhiker's Guide to the Galaxy was published(n also a movie).
Iv been mostly loyal to Lee Child(borrowed from library), Steven Brust(same), Jim Butcher(same), LM Bujold(same but Vorkosigan only mostly). Eddings, Anthony n Donaldon I read n bought from the early 80s(mid 80s for Anthony) until some time in the 2000s/2010s I think.
I mostly hvnt tried new-ish(or new to me authors in the 2020s except a few): Ada Palmer, Claire North n iv been wanting to read Martha Wells' Murderbot for yrs(even before the tv series, just hvnt yet), Aliette de bodard(
tho only a very few Xuya tales) n between 2000-2019 I tried many authors borrowed from library including Naomi Novik, Stross(Merchant Princes), Paul Park, Stephen Baxter, Paul McAuley, Ken McLeod, Peter F Hamilton, many others but I wanna mention Scott lynch n Steven Erickson the author of malazan pentalogy(which I nvr finishrd)
George rr Martin before 2000(in or around 1997/98), Patrick rothfuss n others during the 2000s/2010s I read many loyally even Terry goodkind.
Terry Pratchett from 'going postal' forwards till he stopped(died).
Kpop I listen on spotify/youtube mvs/performances. I hvnt spent money on kpop(unless ur count trial version of spotify) so my loyalty is quite suspect to outsiders, tho I stan those in my sig with my listening, attention n even on my blog(which only has 2 posts abt SNSD in 2018).