I’ve NOT replaced mine based on an inspection from a reputable sail loft. The sail maker inspected both my main and jib. It was his experience and recommendations that I most sought and appreciated. Based on his inspection, he assessed their current condition, estimated life remaining.... and most valuable of all, his recommendations and options. For my sails, he recommended some repairs to my main, including releasing the bolt rope and adding a second reef point. He recommended replacement if my jib UV strip. He estimated a remaining life of 8 years!
If you haven’t done so, I recommend having your existing sails inspected by a reliable sail loft and make your final decisions based on that.
I apologize in advance if my post appears presumptive. BrianW