You're allowed 24 hours to submit your answers, so 10 hours isn't bad.
I think the key is to take lots of breaks and allow yourself some time to think and check your answers over.
The last 24 hour exam I did required lots of reports to be printed off so I just did one report, read it, had a little break and started the next report and I didn't submit my final answers until about 22 hours in!
I think they give you such a long time so that you don't have to try to rush.
Best of luck if you decide to re-sit your exam!