I do the same thing at about 90% of my sweet 16's and 2/3 of my wedding. However, once in a while I get an older crowd, or a crowd where more music in a shorter amount of time isn't a good thing if they're not exposed to a lot of the current music. For example when I was in PA last week in stroudsburg... that crowd didn't know much top 40 and was mostly older, so I didn't quickmix as much. Whereas one week later... older couple again (groom was 40 bride was early 30's), most guests were 30 and older, but they were major partiers, and being that I was splitting time with a band too, I quickmixed just about every song. and must've avg'd less than 90 seconds a song. In that crowd I had 4 past weddings and 2 future weddings in attendance, so clearly that's a style that this circle of people appreciate and are comfortable with. In fact, I just had a meeting with a couple last night who's in the same circle of friends (they weren't at the wedding due to other commitments), and they said to make sure I don't let the songs drag out and that although they know I don't usually do it, they want it to be clear that they don't like that in case I wasn't sure.
In mix's case I'm not focusing on the quickmixing though... im simply emphasising the knowledge of current music. Adj2ent rightfully said that there are events that exist where knowledge of current music isn't necessary, but if mix wants more events and/or higher paying events, something has to change, and it will most certainly start with expanding his knowledge of music.