13 episodes is perfect. Doesn't give them long enough to get tedious.
I don't think it was ever a problem of tedium, but that it was blatant how much they were just winging it as they went along. In a way, the show was a victim of its own success. It was a big hit for NBC, and therefore NBC was unwilling to do anything to risk losing that. So, instead of having different characters every season, the writers were stuck with characters they just really didn't know what to do with, which is why we got Sylar going on a roadtrip and Hiro's amnesia. Even with their idea to have 12 episode "books", they just rapidly changed storylines, abandoned others, and just went all over the place.
NBC needs to stick to the 13 episodes and not do one of these "Well, it might be a miniseries, but if it's successful, we'll keep it going!" If they want something akin to the first season, they need to be able to tell a complete story. If the show is a hit, then go with the original plan of telling a new story each season with new characters. But, NBC being NBC, I wouldn't be surprised for them to do the exact same thing and be afraid of making big changes within the show, particularly since they are far more desperate for hits than they were eight years ago.
Did the original series have any sort of conclusion? I stopped watching somewhere in season 2.
If I recall, the show ended with Claire revealing to the world that heroes exist, which actually wouldn't be a bad point for them to pick up from.
