If the house is 12 years old and there hasn't been a problem, then the fittings have been connected properly. Most of the system problems were from incorrect fitting connection. This still leaves the possibility of hardening of the tubing, especially on the hot water lines. It is better to replace the tubing with copper or PEX as soon as possible; before a connection lets loose and renovation is required. The choice of purchase now depends upon whether you want to do a $3000 tubing replacement job and still feel you have a good buy.