Several years ago, SSD's had a lifespan of a couple years. These days reputable companies such as (Samsung etc) build these with such quality that they now have a lifespan of approximately 5-10 years. To the best of my knowledge, HDD's are known to last for about that same time, depending on usage. And yes, SSD writing shortens the lifespan but doesn't necessarily kill it.
There are several factors that you have to consider such as the quality of the drive to begin with, how full it is, and how much usage is being applied. For some higher end SSD's as of 2014, some manufacturers are saying they will last you your whole life, but I wouldn't bet on that; However, it is safe to say that SSD's these days can now live as long as HDD's under reasonable conditions.
Lastly, the only downside for hybrid hard drives I see is that when new data is being written, it acts like a HDD. The only time it would act as fast as an SSD is when it caches that information which can be difficult for some users because it can be tedious to configure. For those looking purely for speed, an SSD is the way to go. For those who don't want to mess with multiple drives, then Hybrids are the way to go, and if those who are short on cash and would like capacity, stick with good ol' HDD's. ~Good luck!