Here is a biased timeline for when you should have a Z.
1. 18-22 -- rich or parents bought it for you. Go for it
2. 22-26 -- pay off your damn student loans first
3. 27-33 -- first good job after college -- Z time
Branch point M = Married S = Single D = Divorced
33-38(M) -- buy furniture, curtains and a minivan -- no Z
33-38(S) -- buy video games and a motorcycle. Got a garage? Get a Z
39-48(D) -- wife took furniture and curtains -- still got garage? Get Z
39-48(S) -- take a social skills class and get a date (jeez are you picky or just ugly)
Branches Merge
49-60 -- tell kids to pay for their own damn college -- get a Z
61-70 -- tell grandkids to pay for their own damn college -- get a Z and a Porsche (80-89)
