Just an anecdote, but many other studios that run online servers have commented that regular maintenance times are usually very generous so as to be able to correct any potential hiccups within that window when it comes to implementation. I'd say 95% of maintenances only take 15 of actual work max but sometimes there are problems that stretch this to 10X as long so they can still fix and be within estimate. It's like telling someone to be somewhere an hour before you actually want them there so they are much less likely to be late. I also don't know how often Aigis comes out of maintenance early if things are smooth, many do but some games always wait until specified time to bring server back online. Probably depends on level of overall traffic around that time.