As with anything that is related to cooking, the time it takes to actually steep your tea is going to vary based on the tea that you are steeping. For the most part, large leaf teas are going to require a bit longer than finely cut teas such as herbal, green, and black. But, you need to be careful with some types because if you brew them too long, they can become bitter. Black tea is a perfect example as it is probably only going to need around five minutes or so to brew. But, even a few minor minutes after this and it can begin to become bitter.
For other types such as green and oolong, they will not take quite as long and can even be done within two to three minutes. Whatever tea you are steeping, do some research (or look at the package) to see how long it should be brewed for.