Young, Middle-aged, Old, ... ??
Judging by various reasons given in other threads, it is more likely a function of
"when my XXXXXX died, I started ...... "
Where XXXXXXX is the relative who died and made you start thinking about family, and where did we come from, etc.
I am 58, and I started about a year ago, when I went throught the various papers and photos from and about my Grandfather, which my Grandmother left me, when she died.