The only time, in my experience, where double clutching helps is when you're driving a car with a transmission with weak synchros. My brother's old Nissan truck had a worn tranny with a crunchy third gear. Double clutch and the crunchy didn't happen nearly as often.

Clutch wear comes from the friction material being scrubbed off when the clutch is slipping, i.e. on take off. Double clutching is only going to multiply the potential slip events that the clutch "sees", and thus possibly shorten the clutch's life but only make things slightly easier on the transmission.

Most modern passenger car and light truck transmission do not need to be double clutched except under specific circumstances. Everyone else has pretty much said it, but I'll repeat it, synchros eliminate the need for double clutching.

Pretty much no one that I know in motorsports double clutches. Takes too much time.