This is a very simple override mod that band-aids an issue in EA's code. With the Adventure Awaits pack, imaginary friends are presumably only meant to age up when you decide that they should by using the "Offer to Make Real" interaction once your Sim becomes a teen. Due to an oversight by EA, imaginary friends seem to be treated as an unplayed household when they are not yet added to your active household. This bug seems to happen even in vanilla games that have never been modded.
Because of this, if you play rotationally and you have your Aging settings set to "Auto-Age Unplayed Households", your child Sims' imaginary friends may age up unexpectedly while you are not loaded onto those family's lots. This seems to cause all manner of bugginess with them when it happens, as they are not intended to age up in this manner.
This mod will prevent imaginary friends from aging randomly, but they can still be aged up as directed by the player using the "Offer to Make Real" interaction.
Pack Requirements:
Requires the Adventure Awaits expansion pack, because otherwise you don't really need this.
Notes:
This has been tested and seems to work for its intended purpose, but has not been tested extensively yet. If you still see any aging-related weirdness with imaginary friends after installing this mod, especially in an otherwise unmodded save, let me know in the comments.
This mod will not fix the other bugs inherent with imaginary friends, of which there seem to be many.

