> enough to host whatever outside AI that we need for the coming 15-20 years.

Not sure who "we" is, but I highly doubt you'll use those servers for 15-20 years.

We run production on servers 15 years old for our company/clients. Servers now are far faster and the software barely changes performance characteristic wise. We run Java, Perl & PHP ERP/departmental type projects; nothing that gets added makes anything slower and I don't see that happening either. Unless clients will want vastly different things, which, you know, they won't as they are big sluggish companies.