If Marty didn't have that 6-game burst that ended as abruptly as it started, and had a season of save% in the .880-.890 range, there'd be a lot more fans calling for him to hang 'em up. Those 6 games bought him a lot of currency this season (because deep down, Devils fans still want to see him succeed, see him have one more shutout, one more burst of games where he looks like Marty of old). The fact that the Devils happened to win some of his more "meh" games bought him even more currency with PDB. But yeah, the last 11 games for Marty have been rough, most of the last 39 games have, and all signs point to him no longer being effective sooner than later. He's a former .340 hitter who now hits around .220 but has an occasional 4-for-4 day, or a 5-for-12 burst. Those are fun to watch when they happen, but they require getting through a lot of 0-fers.
Even WITH the out-of-nowhere hot streak Marty had, his save% over his last 39 games is still just .896. That would rank him 43rd out of 46 qualifiers this year in save%. That's not really sufficient. And like Tri pointed out, Heaven forbid Schneider ever got hurt next season. You might be watching something not much better than 2013 Hedberg if Marty was forced into being the starter. I definitely don't ever want to see that.
It's really easy to make arguments when you get to selectively pick which stats count and which don't. Take away Marty's 6 worst games this season and I bet he looks great. If you are going to make an argument based on stats, let them speak for themselves, don't cherry pick.
His season totals this year are more then fine for a back up, IMO. (I am sure I am sounding like a record at this point so I will try to stop re-iterating that point)