It would appear that if you want to live long while retaining all your faculties, you should take up the study of Sheldru, the cant spoken by Irish travellers. Micheal Mac Enri from Co Mayo went to God at the age of 102, and Paddy Greene, the schoolmaster of Ballinalee, Co Longford, the greatest living authority on the subject, is in his 98th year. He visited the department of Irish folklore at UCD last Christmas and in his talk showed the vitality of a man of 40.
Master Greene's contribution to the collection and study of Sheldru is acknowledged in the handsome reissue of R.A. Stewart Macalister's The Secret Languages of Ireland, first published in 1937, and now available in facsimile from Craobh Rua Books, 12 Woodford Gardens, Armagh, £27.50 sterling including postage. If I may refresh your memory, here are Macalister's essays on Ogham, Cryptology, Hisperic, Bog-Latin, Bearlagar na Saor (the secret language of stone-masons) and the cant known variously as Shelta, Sheldru (the correct term), The Ould Thing, Minker's Tari (Tinker-speech: their term, not mine).
Kuno Meyer supported the contention that Sheldru is a secret language of great antiquity, formed on the basis of Irish at an early stage of its development. He further claimed for it a close connection, if not an identity, with the secret tongues referred to here and there in Irish literature - but you must read Macalister for an analysis of this contention. To whet your appetite here's The Lord's Prayer in Sheldru, taken down in a riverside tent from an Irish travelling man in 1890, by Dr John Sampson, the University of Liverpool's librarian. I give Sampson's word-for-word translation.
Muilsha's gather (I's father), swurth a munniath (up in goodness), munni-graua-kradi dhuilsha munik (good-luck-at-standing thou's name). Gra be gredhid shedi ladhu (love be made upon earth) as aswurth in munniath (as up in goodness). Bug muilsha thaloskminurth gostha dhurra (give I daynow enough bread), Gretul our shaku (forgiveness our sin) araik muilsha getyas (like I forgives) nidyas gredhi gamiath muilsha (persons to do badness I) Nijesh solk mwi-il (not take I) sturth gamiath (into badness), but bugmuilsha achim gamiath (but take I out of badness). Dhi-il the sridug (thou the kingdom), thardyurath (strength) and munniath (and goodness),gradhum a gradhum (life and life), Amen.
My regards to Master Greene, Nus a Dhalyon dhuilsa, old friend.