That sounds really brutal. Super Mario games were considered hard and even they had multiple checkpoints in most of their levels.
It isn't really. Tho it seems brutal for once per 5 levels. It really isn't because even if you die on the first level you can know how to beat it immediately or maybe after a few tries. The thing is if you add a checkpoint right after that it's the same thing as it doesn't really become a challenge at all as every level is the basic trial and error and is quite easy, but if you do multiple checkpoints after maybe 3-5 levels if you want to be more forgiving, then it gives a sort of challenge and makes it more fun. (Damn that's long and btw if you think 5 is too much then do 3 since it still gives challenge)