That's often the concern voiced by our customers when they see a saddle with serge panels. Back in the day, English saddles had serge panels; at some point (and I'm still researching to find out why), leather became the material of choice. And while leather panels are still the norm, serge is gaining in popularity, and with good reason. Serge has a lot of benefits: it breaks in more quickly, it helps wick sweat and dissipate heat, it's lighter weight, it helps keep the pad from slipping, it dries quickly, it can be a big help with a sensitive or "cold-backed" horse ... and it wears very, very well.
How well? Ok - remember the "Black Country Rocks Customer Service" post I did a couple months ago? (Click here if you need a refresher.) Remember Jenny Kimberly's Black Country Equinox - the 4 and a half year old saddle that's been ridden (by a conservative estimate) more than 6800 miles? Take a look at these photos, and you can see for yourself how well serge panels hold up, even under some pretty extreme conditions.
Six thousand, eight hundred miles down, and a LOT more miles left in it. That's a pretty convincing case for the durability of a serge panel!