RatStar is right as far as age not effecting growth.
I wrote this post in another thread, it might *maybe* help
"When I'm not able to check up on 'bubby' I go to the time screen then press the first and third button at the same time (this makes it so that you can change the time settings.) While the time is being changed your tama stays the same. It's like pause (I have no pause on mine either). My sister showed it to me and she actually had hers on the change time page for about a month (that's when she gave it to me to play with ) If you want it to age you just change the time to later in the night, and then change it to day time and it will age, but it wont speed up the growth process. You can have a 21 year old baby if you did it long enough "