Hummhumm. That, I'm not entirely sure of. I think it's about two weeks for a generation to move up on the evolution chain.
Here's a great website that shows all the Evolving Items and which ones are currently fully evolved and what poses they include, but they don't show which generations are where on the cycle. So I guess you just have to search for that generation and look to see whether it has all the poses yet (or at least, the poses that you want). http://www.tektek.org/gaia/evolution
Awww. -Pats on head + feeds a sugar cookie- 4laugh That's m' girl.
Ah! It's ok. c:
Well. Not all items age.
The item you're questing for is a special kind of item called an Evolving Item. These items 'evolve' over time, and as they evolve, new poses for those items are unlocked. The old ones become unavailable until the item completely finishes evolving, at which point all the poses are available.
Later items reach this stage of total evolution - well, later. So a 3rd Generation Evolving Item is going to be completely evolved before a 7th Generation of the same Evolving Item is. Do you understand?
Using the same example, once both the 3rd and 7th Generations of that same Evolving Item have totally evolved, there isn't any difference between them and how many poses can be used. However, for some reason, some fully-evolved Generations are more expensive than others - maybe there's less of them, and sometimes people just like the 'status symbol' of owning a First Generation Evolving Item.
New generations of the Evolving Item are sold at the Cash Shop for Gaia Cash. The Evolving Item being sold in the store changes to the next Generation every time the original Generation gets an update (you can usually see those in the News section). When the original (or first) Generation of that object completely evolves, newer generations usually stop being sold in the store, and the older Generations continue to age at a set rate (eg. once every two weeks) until they all reach complete Evolution.
The different Generations are at different stages of the evolution cycle.
For example, say that there are three Generations of a specific Evolving Item in existence. The original Generation will have the third set of poses available - the Second Generation will have the second set, and the Third Generation will have the original first set that the object came with. Still with me?
Some people, like myself, don't mind buying a newer Generation and waiting until it finishes evolving or grows to the state where it has the pose I want. Other people, though, dislike waiting and instead save up for the Generation which is currently aged to the pose that they want. This can sometimes be more expensive, so it's up to you which one you want to go for.
Sorry if that explanation was way too long. If you have any other questions about Evolving Items (or just Gaia in general), I'd be glad to help.