Hey MLG,
It depends heavily on the individual so I'll use myself as an example.
When I was your age a deck of bicycles would rarely last me a day. Within a few hours they would be clumpy and the edges would start to wear. Using playing cards was particularly expensive at the time and most of the money I made went into the cards I used to continue practicing.
As time progressed I realised playing cards are not all made equal and better stock often leads to a longer lasting deck at some expense. Some decks would last me a couple of days and others a few hours.
What I've come to know now, as I've aged with cards in my hands, is that it often relates directly to how oily or sweaty or moisturised your hands are. When I was younger my hands produced a fair amount of natural oils but now in my 20's this has subsided and a deck of bicycles can last days and other decks can on occasion, last weeks.
In my struggles with having cards last as long was I could I wasn't able to find a reasonable way to clean them, but I did find ways to make them more affordable (buying in bulk, buying Costco bikes etc).
With my hands at your age the art of cardistry deck would have lasted 3 days to a week, now it would last me 1-2 weeks.
Hope this helps and keep at it!
B.