The recent Paris-Tourmalet 1000 UAF started at 09:00 Sunday and finished midday Wednesday with daily distances of about 240, 300, 330 (because of hotel location) and 140km. At no point did the peloton ride past midnight with 1.5 hour lunches and dinners and hotel beds each night (from memory, 5-6 hours sleep each night). The route and weather was reasonably benign, which helped, but a couple of early starts were needed.
Whatever way a long brevet route is split up, somebody's sleep preferences will be disadvantaged. As long as the organiser/s has put some thought into the problem (e.g. balancing daily distance to available sleep stops, sleep deprivation, accumulated fatigue, traffic intensity/ hills on some roads) and let potential entrants know what the deal is beforehand, pretty much every start time is fair game.