The thing with liveaboards and the rhythm of the dive day is that there are generally two deep dives early in the day and then a series of progressively shallower ones. I have, unfortunately, just been dealing with one of my divers having got bent (Type 1) on a liveaboard here in Thailand after only a day and a half of diving (he's done with his chamber treatments and is flying home tomorrow). The chamber tech (who is also a dive pro) and I sat with him for a while and discussed what he can do to attenuate future problems (the doc has indicated that he will be cleared for future diving with no restrictions).
Now, here in Thailand we have "only" four dives a day on our liveaboards, mainly because our dives are rather deep, on average--significantly deeper than the dives in the Caribbean in my experience--and our divers simply get too short on bottom time by the end of three dives to do anything but a shallow and short-duration sunset/night dive to round off the day. My diver apparently actually got bent on the first day, when he thinks back on his symptoms in hindsight, but really only got recognizably symptomatic after his 6th dive--his second deep dive of the second day.
The upshot is that a "skip the third dive" or "skip the third day" rule is perhaps comforting, but may not actually work. If a diver were to follow that rule here, s/he'd have two deep dives and skip the shallower afternoon dive. What can help here is skipping one of the two morning deep dives and cutting down to "just" three dives a day. What can also help is diving nitrox on air tables (without violating the MOD, of course). Long surface intervals help (which is what you get when you skip that second deep dive of the day). And, clearly, skipping a day of diving to offgas can also be a big help. Because on a liveaboard you will have to make hard choices about what to skip, it might be more workable, as Vlad proposes, is to cut down to two dives mid-week, skipping not only a deep dive on the two-dive day, but also the night dive the night before, making that a three-dive day rather than four, especially if it's not a really thrilling one (most of our night dives here aren't that great, and I'd happily skip 75% of them).