How important is it to cut my nails on every Erev Shabbos? What if I cut them just once a month when they are long?
It is a Mitzvah to cut one’s hand nails on every Erev Shabbos. This is to be included within one’s Erev Shabbos preparation list and applies every Erev Shabbos. This is based on both Halacha and Kabbalah and is considered close to an obligation. One should not wait until they are long in order to cut them.
Sources: See Admur 260:1; Michaber 260:1; Kol Bo 35; Rabbeinu Yonah Hayirah 309; Sefer Chassidim 58; The severity of this Mitzvah: Elya Raba 260:4 records a Midrash which states “There was once a Rabbi who passed away and appeared to his students in a dream with a blemish on his forehead. He told them this is due to his negligence in speaking in middle of the blessing of Meiyn Sheva and Kaddish, and due to him not being careful to cut his nails Erev Shabbos”. This story is also recorded in Sefer Chassidim ibid and is brought [without the conclusion of the nails] in Admur 268:17 and Taz 268:9