Purge/release RAM during rendering
When rendering in After Effects, the RAM is filled up to it's maximum (if needed) and then continues to cache to disk. This usually makes the computer completely useless for the time After Effects is rendering and until RAM has been purged afterwards.
Why not purge/release the already rendered frames? Not only could the computer be used during rendering to some extend but this should probably speed up rendering as well.
Antoine (Autokroma.com) commented
I think it really depends on the project, sometimes frames are needed in some other place in the render. What you could try is running aerender with limited memory available