I can tell you precisely - 5 minutes and 35 seconds. That was the length of the song I used to walk down the aisle to and it literally ended on my last step, right next to Will. Pretty cool that it worked out that way, I didn't plan it...lol
I walked down from the spa and waited out of sight before the music/ceremony started. There the groomsmen were waiting (also out of sight from guests). The song started and 12 people walked out ahead of me, I met my father at the bottom of the stairs and proceeded to the end of the aisle. You can use a longer song, 2 songs, or just pick up the pace if you want everyone to get there faster.