It actually is quite healthy but naturally, drinking lots of cups of coffee everyday will not be suggested. Even drinking a lot of water can be bad to the health. Perhaps a couple of cups of coffee and tea would be great and helping body to operate in a better way and then whenever you are thirsty or want something to drink, try looking for pure water which is the best solution all the time in the history of mankind. Of course this is great that you are even concerned about drinking coffee and the effects.
It's always great to know what to eat and drink on a daily basis. Caffeine is definitely useful for human bodies but excessive amounts may have its own effects and rather bad consequences. When you are forcing your body to stay awake by drinking coffee or tea, that is a bad move because body needs to have its normal functions with no forced prescriptions. Of course I can guess that sometimes, especially on exam nights, perhaps it is needed to stay awake for a couple of more hours.