I met someone who lives outside of Israel almost full-time and who told me that, because he's in Israel for each of the shalosh r'galim every year, he keeps only one day yom tov. Is this (the applicability of that criterion alone) a valid halachic opinion, and, if so, whose?
Rabbi Shlomo Zalman Aurbach rules this way in a responsum (Minchat Shlomo 1:19:7). After reading it I'm not sure if he also requires that they own a permanent dwelling in Israel to live in during Chag or not; CYLOR for a final ruling (as usual).
As far as I know the Puskim used to distinguish between a married man / woman to a single man / woman.
The point is whether the visitor has a chance to stay in Israel or will he defiantly leaving Israel after the holidays. Since a married person will probably gat back abroad he needs to keep the second day as it is his community roles that he needs to follow.
As for a single person, since there is a theoretical, reasonable chance that he will stay in Israel, the most of the Poskim (החיד"א, הרב עובדיה יוסף, הרב משה פיינשטיין ועוד)
So if you are single you can keep only one day and you have "Al mi lismoch".
BUT I have to mark that there are Puskim that don't think that any one should keep the second day, see here : link.
You can find here a full thread on this issue: link