I actually don't cube as much during summer vacation as I would normally do because I go to the beach or Engineering at my high school. So my times actually stay that same, if not decrease.
My first summer I dropped down 3 seconds but was disappointed in myself. This summer I have a boatload of stuff planned but will learn ZBLL. Last summer I basically learned a whole bunch of useless algs and this summer I plan to make this learning more constructive.