The fragrance lasts quite a while, but our rule of thumb is to only use waxmelts for about 24 hours total. After that, the old melt is thrown away, a new piece of the tablet or even two is broken. Some tablets can last even longer depending on the scent, so let your sense of smell decide!
If you don't know how many pieces of the tablet to break and use at once, start with one, wait for it to melt, then see if you want to add more; you should be able to figure it out in about 15 minutes.
It all depends on how much fragrance you want to feel in the room. One piece is often enough for a small room, such as an office or bathroom, and two will usually fill a larger space, such as a living room or large bedroom.
