Considering Red can be challenged again every time you defeat the Elite Four, then regardless of my opinion, the player still has the opportunity of battling Red more than once. It makes easy training for the game player and for those who enjoy having a rematch with the strongest known trainer in the game it's worthwhile.
Although, if I could choose, one battle against Red would have been sufficient enough for me. He's a special character in the game, and if I got to battle him over and over again then it would become dull after an x number of times. I know what his strategy would be like and I know what his team would be like. Plus, I would only be getting stronger, therefore making the battle less of an experience.
The journey up Mt. Silver is as long as it is, but the Elite Four has always been good enough for when I wanted to easily train a Pokémon. Not to say I won't challenge Red possibly twice, but I won't overdue it just to train a Pokémon of mines when there are other routes to take in doing so. If it's just to battle him, then it's different, but I would prefer not to overdue it or else, again, the challenge would become less of an excitement.