I figure what was good for the majority of bikes and riders in that period is fine for me now. I'm just talking vintage steel road bikes for now, and 170 mm 172.5 seem to be the most common lengths. So I am not straying from that.
I imagine different styles of riding, type of bike and era could come into play with crank lengths. The next crank length I'll think about then is late 80s 90's MTB pre-weird suspension cat. Man I miss my MB2 lost it awhile ago left at an apt.