Originally posted by JHD Point taken at the wide end - but on APS-C if 9mm matters between 31 and 40, that is going to depend on the individual. I just sold my Sigma 30/1.4 but kept my DA40, so I'm well aware of the difference 9/10mm off of 40 makes. Now if you prefer primes to zooms, you're going to be packing a whole lot of lenses at that rate. Not very practical or convenient, especially given the quality of zooms now a days.
I will generally take the DA 21 ltd, DA 35 ltd and FA 77mm ltd when packing light with maybe the FA 50/1.4 in there and often run 2 bodies, maybe 3. I also have a manual focus line up. With film, I have different line ups which vary depending on af or mf.
Edit: When I was a kid, my grandfather taught me to start out with the most used prime. The 1st added lens should be about 1/2 the focal length of that and the 3rd one should be about 2x that. That logic would make the DA 15/4, FA 31/1.8 and FA 77/1.8 a nice, fast set. However, I like my 21, 35 and 77 ltd setup. I also have the DA 40 and FA 50 in there with an A/1.2 lurking at times.