I found the 1st book by chance at a book warehouse sake sometime in 1997/1998 I think. The other book I bought then was the History of The Lord of the Rings: drafts of Fellowship of the Ring(by Tolkien, edited by his son Christoper: 1st of 3+ books in the History of Middle Eath series).
I read n reread the 3 earliest ASoIaF books a few times for the enjoyment/satisfaction I derived from reading those 3. I tried to reread after the 5th book was out but stalled due to work/tiredness/brain too overstuffed from watching tv/movies/Comics n other new-ish books(I wrote a draft tat disappeared mentioning Reacher, Dresden Files, Riftwar, Bones, Dragaera, Vorkosigan, Grisham books ard then/after; except for Bones I stopped midway[Riftwar I read when out originally but stopped after original& Kelewan books] reacher, Dresden, dragaera & vorkosigan I started late when I could borrow from library(physical and/or digitally). If I waited till any of above complete I'd be waiting still. Rowling's Potter grew exponentially by readers not waiting till series was complete. I understand readers not wanting to start an unfinished series but if everyone did tat for Harry Potter or Wheel of Time, Rowling n Robert Jordan might nvr hv grown their readers/sales until they could finish their series.
As for Martin: if he could hv an income whole he wrote Asoiaf as Tolkien taking 20 yrs to write(or at least between hobbit n lotr), he might hv started but who knows where it would hv stopped without readers/sales/feedback. History of middle earth: return of the shadow is fascinating on the drafts of fellowship of the ring; for me at least I had/hv the experience of reading Asoiaf 1-5, dunk n egg 1-3, n other works by Martin. None of it is negatively impacted even if the winds of winter is nvr completed. Mazatlan is touted by others as complete but I nvr finished gardens of the moon(only cos I nvr bought it n had to return my library copy mid reading n no copies available to pick up where I left off). If i tried now I would read it digitally but 10+ books puts me off. Similar for tad Williams dragonbone/sequels. Wheel of time I couldn't get past 1st page so nvr borrowed it.