Read some reviews....
They don't look promising.....
I read several reviews on Amazon and with the exception of one reviewer that drove 2000 miles towing a trailer in his Volvo, the other reviews were all 5 stars. Even the trailer hauling Volvo driver got 20k miles before he replaced them. For me, 20k miles will be a little over 7 years from now.
As far as replacing the Coil Springs - if they aren't broke, don't replace right? Although they can be hard to find, I did find OEM for around $93 each.