The thing is monoglot comes off like he is just desperate to use the offer whether he has any need to or not. Purposely overspending to use a 0% offer is just moronic. The money still has to be paid back.
Now, if one has a large PLANNED expense and wants to use 0% and knows they'll PIF in time, it makes perfect sense to utilize the offers. But an 18 year old looking to overspend is just going down a bad road IMO. (Plus he already said his QS is at 50% util, so worry about paying that vs creating new debt)
I have run a card up to %50 or even %100 util but I always paid it off before I carried it into the next statement so while I am sure it put a dent in my credit that month, it didn't stick around for long. I would never want to carry that high of a balance with a %0 promo as I wouldn't want a big fat red flag like that hanging around.
I think even if he does make a lot doing accounting or what ever (I doubt it knowing what most of them make even with 4 years in collage/ years of real world experience) that it sounds like a bad road to go down. I am sure many of them also purposely overspend to get a bonus that will cost them in interest down the road, make them default on payments or blow there savings if they had any in the first place leaving them exposed to even the smallest unexpected expense.