This is a whole can of worms, people often quote opinions as facts whereas there are no SI's(statutory Instruments) regarding 'change at' dates. The Gas installation and use safety regulation do require that the system is 'safe' to use' . The inspecting engineer has to make an evaluation of whether the regulator and pigtail are 'safe' . Obvious issues are condition, leak tightness and performance and recommended 'change at ' life . The manufacturers of regulators and pigtails recommend various 'change at' intervals , as do the various national and international standards , to which these components are compliant , of which they are a few .I've seen regulators 12-15 years still perform ( lock up pressure, working pressure and maintain correct pressure at high flow rates) and some at 18 months to 5 years old fail - oil contamination due to mishandling of the cylinder or inappropriate positioning with regard to regulator height- yes I do cut open failed regulators to see what caused them to fail.Also had one where the diaphragm had split. Similarly with pigtails , some look like they have just been installed, yet are 10-12 years old. The trouble is we can't see inside to look for internal damage( collapse of the inner tube , internal cracks or perishing. I always note the age and the recommendation based on the type and the standard they comply with , but leave it upto the client to decide. Its like tyres they look OK on the outside, lots of tread left and no visible cracking/perishing , but what's going on inside - are the steel bands still intact??. To answer the OP's question there are two types of 'steel' braided . one is actually flexible stainless steel or corrugated stainless steel made to BS EN ISO 10380:2012 has a service life of 20 years , however the second type is actually HP rubber tube with an outer stainless steel braiding and its 'change at' recommend life is still ten years .This type is often used in residential park homes and the steel braiding is there to protect against rodent attack.Unfortunately the rubber ones with steel braiding dont have the standard they are made to stamped on them so on the gas course, the instructor said to treat them as having a 10 year life.My final point is , given the relative low cost of a regulator and pigtail why wouldn't you change it at the recommend 'change at' age , sure beats a gas explosion.