How long can one sit at starbucks for?

So a lot of my friends study and work at starbucks for long hours. Studying at home gets boring, so a lot of them prefer a change in environment once in a while. I was thinking of doing that as well. Just for a change. I can order a drink or 2, or grab a bite to eat too. Is sitting for 8 hours a bite too much? XD I mean obviously if the space is not crowded then only, otherwise i’d have to move anyway.