A380 F/O rosters don't often if ever get close to 90 hours a month, they're working at 80-85 % of left seat level. And as the rostering computer has enough F/Os to do its job and nobody approaches the productivity level of 92 hours there's less manual fiddling and better roster quality.
If they budget for 10 crews per aircraft they do it by having 11 F/Os and 9 Captains, it saves money and the manager gets 10% when he comes in under budget on salarys at the end of the financial year. High fives and back-slapping on the 9th floor, a job well done.
Compared to the left seat an A380 F/Os lifestyle is not at all bad. And luckily a A380 F/O new joiner can now look forward to many years of these half-decent rosters as the airlines probable future growth based on orders, replacements and environmental capacity suggests upgrade chances won't come before the far side of 15 years, if then.