Guys guys guys. As much as I love having checkpoints and all that, you should never ever design a level that NEED checkpoint. That means it is too long and too difficult. Having a checkpoint will make those levels more tolerable but most difficult Mario Maker levels are just not fun and checkpoint won't fix that problem.
In official levels, checkpoints serve as a massive relief and usually come after larger, challenging parts. Or right before large, challenging parts.
The NSMB series would be an absolute chore if they designed their levels to not need checkpoints. Most of the late game stages basically require them to not be obnoxious.
A lot of levels in SMM would have been vastly improved with checkpoints. There wasn't anything wrong with the level design, they just had a few challenging areas or some time consuming part, and death was too much of a punishment, while adding a checkpoint would be a little bit of breathing room for error.