So what was probably designed with a five year life span was still in use come the millennium when it was rightly expected to be obsolete years before the event ..
Just to add to that, there are companies out there that i know of still running software that was written in the 80's, they have the attitude "if it ain't broke don't fix it", none of the original programmers would have imagined it would still be running in the 21st Century, but the cost of rewriting it all for no significant gain makes it a no brainer for those companies.