This bag is getting worn out. I think it's almost time to buy a new one.
This bag is well used. It's time for a new one.
「年季が入る」は wear out や well used を使って表現できます。
wear out で「使い古す」
well used で「使い古した・よく利用される」
1) This bag is getting worn out. I think it's almost time to buy a new one.
「このカバンは年季が入ってきた。新しいのに買い替えどきかな。」
2) This bag is well used. It's time for a new one.
「このカバンは年季が入っている。新しいのに買い替えどきだな。」
ご参考になれば幸いです！
日本 
