Looks pretty stable and predictable. If you can ever get around to it, check out the workload timer. You can use smartmontools or better yet, HD Sentinel, to reset the timer. Then you can divide the number by 1024 and get the percentage of wear over the period timed (you have to run it for at least one hour -- it does work on G1 Intels, like the X25-Es). I don't know whether the workload calculator just uses MWI or some deeper metric when presenting the percentage of wear over the timed period, but I think it would be interesting either way.