My rule of the thumb would be - if you can&#x27;t buy a drop-in replacement and get it delivered in a week, it&#x27;s outdated.<p>It doesn&#x27;t even have to fail in a software&#x2F;hardware specific way. If your floor collapses or is flooded, and you&#x27;re using old mainframe with code written in Natural or similar, what&#x27;s your DR story? Which actually makes me curious - does anyone know what the DR plans look like for companies using 70&#x27;s mainframes? Let&#x27;s say a critical S&#x2F;370 in company basement? (and yes, I&#x27;m aware that new z series should virtualise that just fine, but in practice... if you lose a mainframe, what do you even do?)