Did mine in one shot, but there's no doubt that it is tiring. Perhaps the ideal scenario would be to do the whole thing on the same day, but with a break between the two parts.
In fact I was under the impression that the test could only be split due to weather or tech problems until I read this thread - I suppose I shouldn't complain as I passed, but it would have been nice to have had the option!
Good luck with your test / tests
