Imo 90sec is perfect it comes really handy while calculating possible KOs . Not only this but thinking of coming mons and thinking of what move to go for next. At times you encounter a Pokemon you haven't battle against before so you need time to check Dex,stats, et.c. . Yes, I know it will give time stallers free time to stall but you can't spoil out thinking time for punishing them rather it will be punishment to us.