Roly, if you really think that an agent would be so unprofessional as to just rush through your query to get to go on holiday, then you maybe shouldn't be sending them a query.
Even if an agent says, "I'm off on holiday tomorrow" it doesn't mean, "don't send queries". All it means is, "You can send me a query but I probably won't get it till January."
Send it now, send it later. If the agent is open to submissions, she'll read it. And if she's a good agent, and professional, she won't be less thorough in her reading of it because she's full or turkey, or Easter eggs, or Chanukah gelt, or . . . anything.
I know we want to control as many things as possible, I know we want to make sure we choose just the right day (should I send it Monday or Wednesday), make sure the stars are aligned just so, but in the end, they'll get to it when they get to it.
If you want my OPINION, just my opinion nothing more, I'd say wait. Not because it will give you any kind of advantage, but because it's very likely most agents won't get to your query until January, and you can take some time before then to do one last go over of your query. Post it here in the Share Your Work section, make sure it's just perfect.
But if you are just so sick of tweaking, send it now. You really can't lose out with this, seriously. Of all the things to worry about . . . not so much this.