After Effects will use as much RAM as it needs to. There's no problem with the number getting high. You can limit the amount of RAM used so that you don't starve other software by setting the RAM reserved for other applications in the Memory & Multiprocessing preferences. I give recommendations about that here:
Yep, I've set up my CS Suite to really stretch out and use lots of RAM and I like that.
Let the other apps starve! (I usually close them down anyway when I am in CS6, except for the web browser.
I just recall from my days as a computer tech that seeing such high RAM usage was often a yellow flag to explore further for possible trouble....
Enjoy your day, matt
Beware. You do need to reserve some RAM for other software This includes the OS. Follow the recommendations in the document I linked to.
OK. So far so good, but a word to the wise is sufficient.
Duly noted, maestro. matt