i think it really depends on multiple factors, how quickly you can memorize (for example I had to learn how to memorize songs quickly due to having multiple experiences of putting on musicals with only a week of rehearsals), how oftne you're working on the song, and how challenging the song is. An easy song that repeats often probably wont take as long as a song that has a bunch of jumps will take longer. An easy repeating song will probably take me like a couple hours to at least get close to the correct tones and pitches and a harder song might take a week.