distant lands is maybe my favorite adventures card that isn't amulet, and it might be the last card the robots will be able to use perfectly.
it's already difficult to tell when to get provinces, and a lot of the time you just sort of have to have a sense for it, especially in the case of bm. in engines, it's still difficult, but in the event that you're drawing your deck it becomes sort of a simple question of, will buying engine components/payload reduce the amount of turns it will take me to get 5 (give or take) provinces (or foster some other goal, like attacks or alt-vp), or can i get a significant amount this turn? (also the special case where, if i get provinces this turn will it prevent my opponent from 3-piling and winning next turn?)
we don't have any thing like this privilege with distant lands. clearly it is a good card—it is more cost efficient for VP than province as long as you can play it and it gets rid of itself; however, it doesn't advance you in the game, really, in any direction. provinces, when those are gone the game ends and they make it more difficult to do your engine; for distant lands, the first is only 1/3 true, and the second part, it is only true for your first order of distant landses but for the several turns you're getting and playing distant lands, nothing really changes unless you're unable to play some of them.
so when do you start doing it? who knows, is my initial impression. it depends on how good the villages and draw are, if sparing several actions to play them is difficult (see: nobles, ironmonger engines, although it's nice with ironmonger because of the dual-type) then go for it once you think you would reasonably be able to buy and play 2 a turn, but with king's court sort of things you might even do, like 4 a turn, because the engine strength will carry over to provinces, if that makes sense.
@ mameluke's questions: i am pretty confident that DL and duchy is one or the other. DL clearly stands out, to me at least, as stronger if you think you can routinely play them. as well, i am pretty confident that it would be distinct from provinces in a consistent engine, but in an inconsistent one you would get whichever combination you can afford, probably even favoring provinces because of the whole inconsistent engine thing.
i would say that it is as efficient or more efficient than a lot of alt-vp, but it's more of a different sphere that a lot of them because it is much more suited to engine than bm or slog. strong alt-vp enablers like ironworks/$4 will probably beat most of what uses distant lands, but something that can go for DL and then provinces will probably beat, like, any duke-duchy. but who knows.
it doesn't seem like much of a combo card. university, altar, and procession will love it, especially the former, and it seems like a really good third pile for upgrade/rats/fortress and similar combos, and also a good target for ironworks+cost reduction, but other than that it's just a solid engine payload, like monument or something.