Are you bs'ing? How do you manage to play real games if you can't spend 5 to 10 min to play a demo? Don't you know about the sleep mode every DS/3DS has where you simply flip the system closed if you gotta go do something else? Even with the consoles, just set the controller down... turn off the tv if needed... and come back to it later.
I've never needed more than three tries to play a demo to determine if the game was something I wanted to buy. The only times I've ever taken more than 3 tries is for games where I knew I wanted it... but the demo was so fun I just kept on playing it until I could afford the full game (or it was cheap enough).
I could imagine that they might dial up/down the intensity based on the configuration as well as even offer intensity settings the user could configure.
Like with the iphone 7's home button. It doesn't actually click but it uses a 3D rumble style effect to simulate the click and there are 3 intensities you can pick from for it (Settings->General->Home Button). I have mine cranked up to 3... 1 felt too weak.
Still, I would imagine unattached the rumble would be more pronounced anyway just because of how you hold the joycons versus the whole system.
I often play standard games in a window of 10-15 minutes(that's why I prefer handhelds to consoles), but I can save in a full game, not a problem. I'm also well aware of the 3DS sleep mode, and it is complete and utter ass. I can leave my Vita in sleep mode for weeks without it being plugged in, and come back to an almost still full charge. If I put the 3DS in sleep mode, not plugged in, I'll be lucky to get a portion of the day. Once again, why does it matter how I play the demo, the point is, I have to think about it, when I don't on any other systems or handhelds.
This is the assbackwards mentality, and defense of "N" that allows them to do things like this, and think it's OK? Just like the running discussion here about Achievements, good or bad? Why do others care if a feature is there or not, that can be shut off, and never effect their time with a game? I have a problem with the low qty demo's, and by them having a limit, changes nothing in regards to ANYTHING, just them making it "different", for no other reason than being different. It's a demo for Christ sake, it's 1-5% of the game(maybe?), if someone wants to play it 100 times, why does it matter?
As for the HD rumble being stronger with the joy cons detached, I would think that has more to do with them not feeling as strong when the screen is attached, due the the extra weight, as that would cause the rumble to be felt less(as it's causing more stability). So when the joy-cons are alone, the rumble would probably feel stronger, due to not having the extra weight of the screen. So I don't think they would have it stronger or less, base on how they are used(but they may have), but I think it has more to do with the perception of how they felt with and without the extra weight.