it isn't necessary, no. you can build your recall up just as good if you only try to recall your dreams after you wake up (before you start your day). dreams get longer and more vivid as the night progresses, anyway. if you don't already, i would recommend keeping a journal, because that can really help your recall.

if you have any more questions feel free to ask.

oh, if you're interested, there's a tutorial on dream recall in the tutorials section here: (link)