Life span of the PEX tubing is VERY long LONGER than YOU or I will be alive. IF you have a failure it will be with a Pump or Heating unit, OR a crack in the floor heaves up and Severs the line.
Even if you were the MOST UNLUCKY guy in the world WORST CASE scenerio the tube would break and you would see a 'wet' spot on the floor, and your system would be loosing fluid. Simply breaking out the concrete in the 'wet' spot and putting a splice in the line is ALL you need to do. Repour the 'spot' Your DONE.
Pumps will be your BIGGEST maintainence Item. a 100% ferrous metal free system would be BEST CASE scenerio. Bronze, Brass or Stainless pump, Copper Fittings, Plastic etc. As long as you are NOT using a Cast Iron Boiler or ANY Ferrous Metals. You can even use the 'non barrier' pipe. One Tip. Make sure your Pump is installed with the water flow VERTICAL. So the water travels thru the pump DOWN OR UP. IF the water flows HORIZONTALLY air can get trapped in the pump and cause premature wear and LOTS of NOISE! Also DON'T Forget to OIL your pump if it has an Oil point. (Varies by brand) My personal Pref is Grunfos Bronze Pumps. Very Reliable. Very good quality.
Use Compression fittings on your manifolds. Put in an Expansion tank, MAKE SURE YOU HAVE A WAY TO "even" out the flow for ALL of your Returning Loops. DON'T Skimp on a few Valves, your added investment will be rewarded by even heating. If you don't you WILL have 'cold' loops and Hot loops.
