Also I want to preempt your counter argument by sidetracking it a little. If the bulk of your game that is GOOD is way far down the line, even beyond an ENDING and a CREDIT ROLE that's not a good idea. There are plenty of people out there, like myself, who once the beat a "final boss" and "final level" and see a credit roll, they lose interest in the game. This is why before I finish a sandbox game or an rpg I'll tidy up all the remaining side-content in the game, because once I see that credit roll/ending and have the satisfaction of defeating a final level...interest plummets.
Pushmo reminds me of the Mario 3DS problem. I'm sorry Oscar, but I'm not that satisfied by Pushmo. I've been playing it in short bursts for days now, and am 60+ puzzles in and it's still in the "mindnumingly easy and non-satisfying puzzles mode". I'm sure once the difficulty picks up, the game will become a great puzzle game, I like the core mechanics, but after doing a pushmo puzzle 50 times, I've pretty much gotten my fill and my interest in doing more and more pushmo puzzles is almost gone. Maybe instead of each "world" having 16-18 puzzles, they should have had 10 puzzles. Then by the time I'd done 50+ and started to get bored I'd be smack in the middle of the game and middle of the difficulty curve and get some good puzzles instead of still being in the first third and getting ready to drop it.
I think the idea for me, is that after I've done something 50 times, I'm going to be over it and ready to move on to a different game. Saints Row might be a 25 hour game, but it's only 47 missions, so by the time you'd be bored of them it's over. Perfect pacing. Mario 3DS, instead of having 40-50 ten minute levels, has 80-100 five minute levels. In theory it's the same thing, but the repetition eventually kicks in and that's why I dropped it a few worlds into the 2nd half. Sure it was more engaging in concept because it was more challenging, but somehow despite being glued to the screen for the first half, I was really bored during the 2nd half because the repetition of so many 2-5 min levels was kicking in.
You might be different and enjoy having hundreds and hundreds of levels/puzzles. That's cool, a lot of people do. But I get bored of repetition after a while, so I'd prefer games to show their BEST stuff before that repetition fade out kicks in.