System drive: HDD or SSD

I recently put together a gaming desktop. SSD’s didn’t exist, or just barely existed, the last time I built a system. I know that there are only so many read/write operations that my SSD drives will tolerate before they show me their middle fingers, and I have no idea when that might happen but I assume I have a year or so. Anyway, I currently have 2x SSD’s in RAID0 as my Windows drive as well as 2x WD Velociraptor drives in RAID0 as a data drive for file storage. I feel that the HDD’s make more sense as file storage due to their potentially longer lifespan, but I’m going to burn out my SSD’s using them as a system drive. I disabled Virtual memory, prefetching, and superfetch as well as thumbnail caching and the like to minimize wear but I still worry. I wonder if I should run windows off the Raptor drives but there are pro’s and con’s for either option and I can’t decide the best way to go.
Also does anyone know: when SSD’s fail is it a complete, instantaneous failure or do they provide some warning so that one might backup important data before death occurs?