SSDs fail. HDDs fail. If you use enough of them over a long enough time then the question is not "if?" or "when?" but "how many?" or "how often?" ... remember that most RAID implementations are built around mirrored redundancy and recovery, not for pure (gamer-centric) performance gains.
To be honest, a beefy laptop with one or two drives shouldn't really be expected to experience drive failure within the machine's expected lifespan. A consumer needn't worry much about the reliability and longevity aspects of storage media, only the compatibility and price and performance aspects. If a drive fails within warranty then a drive is replaced within warranty, if a drive fails after warranty then it's already fulfilled its rated expectations. I admit I'm assuming no real data loss (the presence of a working backup/recovery strategy), and I admit that (sadly) this might be a foolish assumption.
I agree with above comments, placing OS onto (slow) HDD and applications/data onto (fast) SSD is self-defeating, the performance benefits of the SSD will be largely wasted because the entire system will consistently be bottlenecked within HDD performances. If you want real SSD performance advantages on your OS *and* on your games/apps then you need real SSD hardware for them both to run on ... buy a large-capacity decent-speed SSD and migrate your data onto it, your old HDD can be kept as a backup.
SSD has other advantages over HDD in laptops - they consume much less power so your battery will last longer, they usually generate less heat so your temps will be more manageable (or less limiting), they're a lot more resistant to drops/shocks/impacts which occur frequently on laptops, they don't suffer wear-and-tear from being operated in differing orientations, etc.
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