I don't know about other episodes, but I know for certain there was a spoiler about Eric and Calleigh working together in 'Broken Home'. There's been several mentions of the same thing in other episodes, so I guess we can expect a decent amount of them working together for a while.
And yes, I have noticed the increase all of a sudden, how can you not? I definately think it shows they are planning some kind of follow-up story on Eric that they want Calleigh around for. That has the potential to be really interesting. Not only will we possible get a few emotionally-charged scenes between them, like Jess mentioned before, but worried/overproctective Calleigh keeping tabs on Eric. The thought alone sends me to my happy place.
La la la la-la la la-la!!