You mentioned USB sticks, but I just assumed they used the same type of flash memory that SD cards use?
Aside from USB sticks, any ideas on alternative storage suitable for RPis (something small)? I know you can get eMMC modules that fit into the SD card slot, but I would have guessed they'd have the same issue with writes.
1. Buy high quality SD cards
2. Remove as much disk-IO as possible, using an external USB stick for raw data storage, logs, swap, etc
3. If you really need to make it stable, make the OS read-only