Do you mean how long to learn it or how long to actually quilt it? Either way I would answer, it depends...
If you are using a tight design like Leah Day's fillers, it's a much slower process than say an all over meandering or loops/swirls or loops/stars for instance.
It's good that you are trying! I often read people saying they would like to try it but lack the courage. One will never know if they will like it or how good they could be if they never try! So don't give up!