Originally Posted by k_jupiter
Why would you NOT?
The fixer rapidly accumulates insoluable silver salts, which will eventually precipitate out onto the paper, and (being insoluable) cannot easily be washed away. That is why there are clear guidelines for the use of two fixer baths for archival prints, and why there are limits on how long you can use a finite amount of fixer.
I'm also a big fan of a dilute sodium sulfite bath after the fix, to re-dissolve those little salty buggers before the final archival wash.