What is even luck? (for my friend)

I hope that he get his desired unit soon

TECHNICALLY if he summons 120 times (or 24 sessions) without getting a 5 star, the next summoning session he is GUARANTEED to get at least 1.

....So he could potentially summon another 75 units (15 summoning sessions) and they all be 3-4 stars, although that is very unlikely.

If he is trying to get only 1 particular unit (like winter tharja) I think at the point where he now he is high enough that it would be safer for him to only summon red orbs from now on so he is a lot less likely to get a 5* he doesn't want.

Hope this helps

ive gotten up to 6% before... it really sucks