The slogan of the UK's National Canine Defence League, introduced in 1978 with the intention of dissuading people from giving puppies as Christmas presents. Widely quoted in its original form, it has also spawned any number of humorous by-forms.
A tree is for life, not just for decorating with small shiny objects.
[1998 R. Ray Certain Age 344]
And remember, a pet is for life, not just for Rosh Hashanah.
[1999 Jewish Chronicle 30 July 42]
A Billiard table is for life not just for Christmas.
[2001 Country Life 29 Nov. 96 (advertisement)]
Related to: constancy and inconstancy
Bibliography of major proverb collections and works cited from modern editions is available here.