I thought what can be repaired, should be repaired. It heard one guy said, regarding replacing or retubing a shell and tube heat exchanger, it should last forever if repaired properly. In fact, this guy went on to say that all static equipment should last forever provided repaired properly (I guess to AGAN).
I guess the above view assumes that there is no temperature fluactions which may cause fatigue cycles. In this heat exchanger which is in fact a reboiler, there is somewhat temperatures fluactions occurring especially during trips or shutdowns.
Another case is regarding a PSA (Preesure Swing Adsorption) adsorbers (4 pressure vessels really), the design specifies a life cycle. So it was decided very quickly to replace these vessels upon reaching the specified lifecycle. Even when the OEM said the pressure inviolved is considered low, it will just shoo... according to him when it leaks through the walls whose weld joints were MPI every recent shutdowns.