Mine took much longer than expected, with all the proof readings and all, so don't put it off because it sounds like an easy/short essay. It is very important from what I understand.
Agreed. I sent mine out to friends and family for review once I finished it up. It's nice to get a few extra sets of eyes on it, because what makes sense to you might not to someone else. I think mine was over 400 words, but not by too much. I doubt someone will go in and count them, but don't go overboard. My recruiter said just make sure it fits in the box provided. At 400 words the space was only about half way full from what I remember.
Also, I didn't see if you mentioned your letters of recommendation yet. You should ask for those soon if you haven't already. It would probably be good to get one from a team coach / karate sensei (or whatever they're called :icon_tong). Give them at least a few weeks to put it together.
Unfortunately for me, I gave everyone too long and they just kept putting it off. It kinda pissed me off to hear that they hadn't started within a month after telling them, and then again after I said I need it in 2 weeks, and finally in a few days. A few of them just threw something together in what looked like 15 minutes of rough drafting. I was hoping the LOR's would be a strength in my package, but it turned out to be the worst. So yeah, give them time, but remind them and give them a deadline when you ask so they understand the importance.
If someone asked me to write them a letter recommending them to be an officer in the military I know I would make sure to do my best, for their sake, but I guess not everyone feels the same way.