Good point. I came of age in the lp era and 35-45 feels about right for me, although when I still play lps, 18-20 minutes seems to fly by. For me it is an attention span thing and a perception (not by any means a fact) that beyond say 50-55, you are throwing some filler in there. Lately I have been grooving on the relatively new Bill Evans set called "On A Monday Evening" which comes in at 48 or so and seems perfect. If I want more, I just play it again