During peak times (usually weekends, holidays or when cruise ships are in port), you should pre-order/pre-purchase your tickets and select the time that you want to appear. My visit was during the non-cruise season, on a weekday - I chose my entry 30 minutes after the museum opening time. I was fortunate in that there was no line. Once you are inside, you can stay as long as you wish (up until closing time). The "virtual" karaoke with ABBA is hilarious if you happen to catch enthusiastic fans "on stage".