Should the side effects of caffeine last longer than a few hours?

Everyone's different. The side effects from excess caffeine consumption will vary from person-to-person. Some will complain of palpitations while others will complain of tremors. Most will report increase in urination. The duration of these effects will also depend upon your individual physiology. If side effects last longer than expected (few hours), go see your family doc to be sure there's nothing else going on.