If you want to work over summer ( not that you need to ) then its better to work for 1-2 hrs a day but do this consistently. There's no point doing 5 hours a day for 1 week then getting bored and quitting. Plan what you want to do before each day and try and complete it. As for your PS, Ive found it easier to write a really long one ( like double what your allowed ) but with everything I could think of included. Then you can cut it down/refine it without missing out anything which you might have forgotten.