If it's a new t,couple (fitted and tightened correctly) and a good flame and still keeps going out it sounds like a faulty gas valve.does it keep going off or was it just the once after the new t,couple?
Pilot injector may be choked,does the flame look o.k. the pilot top (popes hat) aims the flame onto the.t,couple can face slightly off or burn through completely. It may be hard to see but does the flame hit the t,couple
Nothing stopping you turning it off ( word of warning, the on/off knob on lineas break very easily). Time to get hw would increase slightly but depending on the size of runs in your house only you can tell.compare that with the money your saving on gas compared to the money on run away cold...