Pi 1 a/b were really fragile but since pi 2 this problem is mostly solved. Still if I need to write a lot I would use a external drive. We have >300 pies running 24/7 on 52 sites all over the world. Even though we use no name brand microSDs we had only 2 failures because of a broken SD card in 4 years. Our partner company was using our hardware as a basis for something. After 1 month they asked us what SD cards brand we were using because they had a high failure rate. Our secret. We use a self made distro with minimal writes, they used default raspian and were writing permanently to the SD card.

Maybe you're lucky or buying the right SD cards?

I've always used noatime for filesystem, journald set to ram logging, etc. Usually everything seems fine until a reboot triggers a fsck. Most were ext 3/4 filesystems.