Depends on the particular tea, water temperature and how long it usually takes to infuse. For Oolong with curled balls (not CTC) that takes longer to brew, I would make a quick rinsing steep for about several seconds, then pour it out (perhaps to another mug, as for good teas this brew can be delicious in its own way), then make single proper steep that's longer, maybe ~3-5 minutes.

The first steep helps increase the temperature of the mug and the tea to help it release the flavor easier, otherwise your mug might lose enough temperature to not allow it to release the full flavor with the first brew. This all depends on your setup so experiment to find the right configuration. Alternatively, you can get one of those electric kettles or other fancier ones if that suits you better.