What fastJehu said is spot on. But with a bit of individual CO leeway.
Granddad kindly CO who has seen real life, had kids, been in the armed forces or had a real job before being a jw.
"8 hours is ok minimum for last six months with a toddler or new baby on board any less than that and they obviously won't cope with all the estra responsibility."
Modern CO who hasn't got a clue, pioneered from school, never had a full time job and follows every word the DO and Branch tell him.
"10 hours minimum with several RV's for last 12 months; wife must be doing well (even with a newborn, depression and CFS!) too. Gotta preside over houshold an 'all."