Having searched high and low several times for datasheets for older 805x derivatives, I'm wondering if it wouldn't be worthwhile to accumulate and store "old" datasheets for these chips before they become entirely unavailable.

Why?

If a chip outdated, what do you need a datasheet for?

I have ~2000 Atmel AT89C55 laying on my office floor since 2001, I am never going to use them (with the exception of a few for repairs), but then I also have a problem throwing them out. That, however is not going to make me use them.

Using outdated chips "becuse you have them" is the road to misery, you find a problem of some kind and contact the manufacturers support to be told to use a current chip. Maybe someone happen to see your product and send you an order for 2000 ea. Maybe you find that tool support has been dropped. Maybe.....

As it is difficult to predict, especially the future (quoting Robert Storm-P) I would never risk using something that is not current.

Now, out of the woodwork is going to come "I have this old stuff and need to add a feature" WHY??? If ths stuff has been areound long enough for the chips to be outdated, throw it out.

Erik