DS3 is also doing 10 including triple science. Most in his school are doing 9 as standard this year.
DS2 did 10 as standard (no triple science) 2 years ago. DS1 did 12, 10 standard plus triple science and further maths. They no longer offer the further maths as the GCSE is more challenging.
mmzz, DS3 hasn't worked it out so thoroughly TBH. He's probably covered everything at least once to a basic standard and is going over areas he's less confident about. Also some parts of the syllabus aren't quite finished yet. I think he's generally much less thorough with his revision than your DS seems to be, but he's been doing an hour a day since January, and 2 hours a day since the Easter holidays started.