such a rich thread, focal length preferences and wise choices- at least they strike a responsive chord. i think we all start out w a normal focal length, 50, and then preferences come through experience. for many years i found the 50 just too normal, and used 35 summaron and IIf as my primary and exclusive set up, and that lens migrated when i went to an m3.
i was amazed by a beautiful color photo by a friend who made it w a 50 'cron on a r5. it made me aware again of the beauty of the 50, but it was probably more about how the artist brought a number of elements together to make the picture that worked so well.
when i put a 50 back on, it almost felt like a telephoto. for someone who preferred 35 for years and never thought they'd have use for a 50, i find the following 50s in my bag of goodies: collapsible cron, current cron, nokton, summar, elmar, as well as another 'cron for my r7. and conversely, going back to 35 felt so expansive and so good, and so normal- i go back and forth between my two favorites, 35 asph and 8 element cron; the 35 elmar is a blast to play with. i traded my 35 summilux back to the guy i bought it from originally.
i never thought i'd go wider than 28...until i put a 21 on, then a certain tom hooked me on the 15 heliar and the vc 28/3.5...
as we gain experience and come across bodies and lenses we can't live without, some come and go, some remain, and some will indeed be passed on to kids and grandkids- i currently have a ltm for each, and i go back and forth about which lens to dedicate to which body, and like frank, my preferred ride is bmw (r100 gs)... i gotta get out and shoot now. ride on!