My understanding, although not the most thorough, is that the general consensus of the Helots in the classical world was that they were a bit of an oddity compared to other slave systems. The standard practice seems to have been enslaving a range of foreigners largely as war booty. The war-captives made slaves came from different ethnic origins, had very little common practices and language. Pair these facts with the vastly different living conditions inherent to antiquity's slave systems (slavery could land you seemingly anywhere depending on your skillset). It becomes apparent that slaves could not go about forming a cohesive social class under the conditions. M.I. Finley (Ancient Slavery and Modern Ideology) argues as much when he wrote: “The slaves, in other words, constituted a type within the larger class of involuntary labour, but they were at the same time significantly divisible into sub-types. Stated differently, the slaves were a logical class and a juridical class but not, in any usual sense of that term, a social class.” (p.77) Thomas Wiedemann (Greek and Roman Slavery, great place to start if you're interested) writes: “The Laconian Helots are the purest example: not slaves, since their relationship was not one of personal dependence upon a citizen household, but one of a community with its own internal bonds of kinship being dependent upon a conquering state (in the case of Helots, this relationship was perceived as one of permanent war)." That is to say that the Spartans essentially taxed their Helots for the produce of their farms and their 'enslavement' was not on an individual scale to any particular citizen, but rather to the state. The Helots were, to my understanding, expected to pay tribute in the form of food so that the Spartans could maintain rigorous training exercises and not devote manpower to agriculture Nino Luraghi in his article 'Helotic Slavery Reconsidered' (I found it a collection named 'Sparta: Beyond the Mirage" seems to agree with Wiedemann in the sense that the Helots don't quite fit the mold of ancient slaves but rather a serf-like class with a fair amount of more freedom than the slaves of Rome or Attica.