Durability depends on riding style and quality of construction.

The 517 is not a freeride rim, so it won't handle lots of big drops. It's a lightweight race/trail rim that will perform great in the XC world. Even so, aggressive XC riders and racers may push the 517 to its limit.

If your wheel is handbuilt, that is a good thing. Handbuilt wheels are more durable than machinebuilt. My machinebuilt 517/LX wheel lasted about 3 months last year (I'm an XC racer). I took it apart and the rim was fine, so I laced it up myself. It's still true and round. I have two other 517 wheelsets I built. One for racing, one for training and trail riding. I expect to get years of service from them both.

Ride your 517 and enjoy it.