Hi Dutchbird,
I'm sure you remember the Meyers (After Effects writers and Motion Graphic gurus). They told me they archive old computers to run previous OS and AE versions on them so older client projects can be worked on without stress. That was a long time ago before they left L.A.
But I think it is a valid idea; hence, I keep laptops as they are in a box. (Lately, this tip helped me open a video done in a Sorenson Codec—nothing the current OS can handle.
So, take care of the old iMac; it might be more valuable than it seems.
My best wishes.