I'm playing tons of households on rotation, so the simyear had to be long. I guess this would be different if I mainly played one house. I have 1 series of 4 seasns each 4 weeks = 1 sim year (28x4=112 simdays).
I play with aging off, turning it back on for New Years Eve only, so I keep full control of their birthdays. Lots of cakes are consumed...
I go by these lifestages:
Newborn/Infant: Age 0-2 (depending on family)
Toddler: Age 2-6
Child: Age 6-13
Teen: 13-25
YA: 25-40
A: 40-70
E:70->
I don't own GrT (yet) so I'm not dealing with milestones, but even if I get the pack I will not care a lot about milestones, as I'm generally not a family player.
I try to stop by each house minimum every 3rd simyear. There might be new sims not really being played as newborn/infant at all.
