Replacing fuel lines 3x times in 12 years is a bit much and if you find it necessary because of deterioration, I would suggest you look source better quality lines. Regular replacement is definitely not a must anywhere near this rate. I have birds that have over a decade on the same lines and besides some mild discoloration there are no issues. A properly installed fuel system will last a looooong time. Regular inspection is good proactive on all components an systems though ...
Based on your other pics i would focus on the following 1st , and use these points as a good principal for any fuel system installation.
- use safety wire and not zip ties around fuel lines over barbed fittings
- never ever use Tygon ( real or imitation ) on Festo fittings
- technically Festo press fit fittings should be used on the the pressure side of the fuel system. where possible, use barbed fittings on the suction side
- drill and screw in fittings into nylon tanks can and eventually will leak.
- use nylon ( festo grade ) tubing where possible over Tygon, and if used, source only real tygon.
- Also in some kevlar/composite tanks, avoid using metal tube extensions that might run through internal baffles. Thesa have been known to "saw" through after many years of use. Interestingly, BVM in the past had found this as an issue that presented itself also because of movement caused by thousands of miles of transporting planes