I have a 99 Lexus RX purchased in 11/1998. It has 152k miles, and the original hoses. I live in California, so no extreme temperatures, and the hoses look great, however I too am considering replacement. Just the preventative so as not to have failure on my wife.. Funny seems in the 60's and 70's you would hear of ruptured hoses all the time, but maybe the construction or rubber is better now, just dont hear of any problems. Still makes me nervous, the unknown secret degradation inside the hose. they arent expensive, but are the new ones better than my originals, who knows...
by the way, at least the bypass hose is not flexing, seems this would make it more durable other than it sitting on top of the engine baking...