Depends on the song.
Some have taken as little as ten minutes to run through the song twice.
Others have taken 25 plus years and still counting.
I'd say don't worry about that just yet. As you continue to practice and the number of songs you know increases, the amount of time will decrease - but will always be influenced by the degree of difficulty, your growing ability, and many other intangibles like your ear, your feel for the song, and in some cases guessing correctly as to which finger and hand positions the original artist used. (I have a knack for doing things the hard way.)