Now we have such small numbers, any bottle lamb would almost certainly be on its ownsome, so we top them up in the field. It works okay, and is nicer for the lamb. But I think that unless your sheep are very milky (like Zwartbles or other diary breed, or our much mourned BFLxShetland Lessa The Wonder Sheep, or Lleyns on unlimited *very* good grass), the ewe's udder does better if she's relieved of one lamb entirely. So if I had the numbers so that pets wouldn't be alone, I'd mostly take one off routinely.
We breed and manage for not-triplets, by the way. Try to mostly not breed from ewes who're from a triplet line, and deffo not if the ewe struggled with the three. And we do the opposite of flushing at tupping time. We still seem to get 1 set of triplets more often that not, out of 5 - 8 ewes lambing!