In your Goonzu journey you will encounter some item that have an expirancy.
Some exemple: any High grade item, frozen armor, flame armor, dragon knight, abel armor, dark knight and vampire armor. (armor here=helm,armor, belt and shoes)
To extend your stuff you will need extention stone (purple stones on the left side of my inventory).
It will let you extend your stuff for 10 more days.
To do so, you will have to take out your equipment part you need to extend.
Open the mix windows from your inventory. Then put your equipment part in the power up box. After, put a extention stone in one of the four boxes below the ENCHANT. Then click expirancy extention and your done!
Don't forget high grade item will not give full boost when the warranty is pass, but it will not diseapear. Stuff with 60 days warranty like frozen armor and up WILL vanish if you don't extend them BEFORE warranty pass.
You can get extention stone from item mall or in market. Alot of ppl sell them in market or on personal shop.