I think both of you missed the point of what he/she said. This is likely to be the last camera bought in part due to age. While I hope that's not true, it's certainly a realistic consideration. Not everybody is an annual upgrade hound (myself excluded).
To the OP, the Kx and K7 are two very different cameras. The only thing they really share is the K mount. Some will say that the Kx has the advantage of a clean high ISO shot and the use of AA batteries (no I'm not getting into that fight again). Others (like me with my K7) say that High ISO doesn't matter. It's more about the feel and build of the camera in addition to the features aimed more at the photographer.
Yes, it costs more but the K7 is a far more rugged machine in my opinion. Someone will likely come in here and say that in 10 years, batteries won't be available for the K7.. Maybe, maybe not. If that concerns you, buy the battery grip accessory and you can use AA for as long as the camera lasts.
The truth is that with either camera, you'll have a tool capable of stellar results. If you go the K7 route however, DO get the WR kit lens with it. It's surprisingly good for an el-cheapo lens.