Doing Duolingo streaks every day isn't too bad, but the most XP you can choose for your daily goal is 50 XP. Maybe some people might think that that is pretty hard, and some people might think it's a piece of cake, but I think that it's way too easy for an "insane" daily goal. In my opinion, "insane" should be maybe 150 XP, considering that each practice will give you 10 XP (so 5 times for an "insane" daily goal). Or at least there should be a really, really insane daily goal. Like maybe 150-300 XP daily goal!
I set my personal goal of 100 xp's a day, which for the most part I've managed to follow but set to Casual 10 xp's in the app.
But yes, it's bizarre they consider 50 xp's a day as being insane. I think these terms show that Duolingo doesn't expect language learners to go very far in the platform... I mean, serious at 30 xp's?
I actually disagree. A high daily goal = forcing yourself to still do it / overly rushing when you have little time for whatever reason, which will ultimately make you lose motivation. While a low daily goal allows you to do less when you have little time. I.e. I had to finish an exam so I've only gotten 16 xp. While for example the next day, when I do have a lot of time, I can do something extra.
Elvper is right: A high daily coach goals like 150-300XP will break your global (and probably individual course language) streak(s) sooner than later.
You can not do it EVERY day (vacation, illness, fell asleep before midnight, busy, etc.).
The best daily web coach goal is: 1XP.
It just means you lose your streak if you don't get the higher goal, nothing else. Some people prefer to set a lower goal for the streak and just aim to do more lessons every day, but others would prefer to lose their streak if they do 140 instead of 150 one day.
Either way we'll do the same number of lessons and get the same XP, it's just about how we prefer to be motivated.