CM Punk should lose because Chris Jericho has beaten Rock, Austin, HHH, Shawn Michaels, Edge, Ricky Steamboat and other Legends in the business. If Jericho loses to Punk cleanly it will hurt Jericho's credibility and wouldn't seem believable.
Hogan defeated Macho Man, Roddy Piper, Andre the Giant, Ric Flair, Yokozuna, Ultimate Warrior, Kevin Nash (with a FINGER), Lex Luger.... and he still lost to The Rock.
Jericho losing couldn't hurt his credibility no more than him being on Dancing with the Stars. He's not this holy god who can't be defeated at WrestleMania... That's Undertaker's gimmick. He's just a guy who plays a guitar and spends time in a ring once in a while whereas CM Punk is a guy who spends all of his time in a ring. Plus, CM Punk is younger. So ideally, Punk SHOULD win at Mania. But that's neither here nor there. That discussion belongs at the WM discussion thread.
Moving on, I don't have a problem with a longer reign from CM Punk. I don't have a problem with even Alberto Del Rio getting a decent title reign. But to be honest, the fans will. Even the ones who are now saying "WWE needs longer title reigns" will be on here by Capitol Punishment saying "WWE needs a new champion." It happened with Orton, HHH, Cena, Batista, and even JBL... what makes you think it wouldn't happen with CM Punk? CM Punk is a great competitor IMO, one of the best in WWE... and I would love to see him put on feuds with a lot of "Summer time" Main eventers like Dolph Ziggler, The Miz, and maybe even get into a program with David Otunga and then cap it off with a match against Christian and Jericho at say Survivor Series.
To me, that would be a full year as champion in WWE's eyes and that would be a great mile stone for anybody. Losing the title then would have given him a lot of credibility and then he could be shipped over to Smackdown to start a feud with Daniel Bryan. Or who knows, maybe by then WWE will have brought up someone like Dean Ambrose to have a small feud with Punk. Maybe even a Barrett vs. Punk rivalry could take place.
Going past a year would be overkill, even for me. Simply put, WWE's seen too much in today's world unlike the days of Bruno Sammartino. So longer runs that expand beyond a year can take a toll on the crowd and can really make things more predictable. But yeah, I would agree that good five month to a year reign would be nice for any champion. Hell, I'd love to see Primo & Epico hold the tag titles until at least SummerSlam, but who knows.