There are a few reasons for this, but simply;
If you WATER FROM THE BOTTOM, not the top, it'll last for months!
Stand the pot in saucer and pour water into that when needed.
Water on top every couple of weeks, to stop soil shrinking in from the edges of the pot, but otherwise, its BOTTOM ALL THE WAY!
And if you're feeling bold...
Pot the whole thing on into a pot one size up and it'll go on even longer!