I don't understand why one would want to use old information or components.
A couple reasons. There's a lot of old powder floating around and it get bequeathed to others who reload. Old powder will not blow up your gun. When powder deteriorates, it becomes less powerful, not more powerful. I have used pounds and pounds of old powder with no incident. and if you have old powder, you would want an older manual because at times they change the formulation.
It's still only a guide and the more references one has, the better. Another reason is that the older manuals have wonderful articles in them that the cheese eaters will not let them publish today.
Lymans older manuals provide data for a lot of cast bullets that are not included in the newer manuals. Besides, there's more to data than powder charges.
Some people are convinced that they are providing downloaded data in the newer manuals for liability reasons. This is easy to confirm one way or the other with older manuals. One simply uses his new powder, and goes to the old manual, and beginning with the start load, works it up and chronys it, then compare to what you got, with what the newer manual says. If you or anyone else wishes to discard your old manuals, send them to me! I'll pay the postage.