There is not going to be a greater tourist option than a B1/B2 visa, and there is a risk with repeated, lengthy visits that an entry or new visa will be denied, based upon the visa holder or applicant's diminishing ties to their nation of origin, as well as a pattern of entry that suggests that they are in fact domiciled, or in the process of becoming domiciled, in the U.S.
It is possible for non-citizens to regularly spend extended periods of time in the U.S., as with Canada's "snow birds" who spend four or so months each winter in the southern U.S., but they have clear attachments to their nation of origin and clear intent to return home. With even longer stays and completely different motivation for the visit, I foresee a lot of potential problems and suggest consulting an immigration lawyer.

