Should I change my cam?!

One thing I’d like to know or have explained to me and maybe others may find of interest is: when does a lobe become a lobe designed for a .904” lifter? What specs determine? One or any combination? Is a lobe one is looking at a fast .842” or a slow .875” or .904” etc? Take away the .842”, .875”, and .904” notations saying it is such, and just look at the adv, .050”, .100, .200”, .300” durations, the lobe lift and if you’re lucky you have specs for .020” etc. I’m looking at a lot of lobes for all size lifters and I see some very aggressive .875” and .842” where the numbers look mighty close to some that are for .904” Slap on a set of 1.6 or 1.7’s and like others have said, have more lobes to choose from. Granted, more complex than just looking at a few numbers in a listing but where’s the dividing line? Just a curiosity of mine.