Its life is around 20,000 pages. Ideally, it should be replaced together when the transfer belt and fuser units are replaced as their recommended life is same as this item. If your transfer roller is worn out, the printing quality from your printer will be not even. For an example, one side(let's say left side) maybe vivid but the right hand side is very light. Refer to the last picture to get some clear idea. This should be replaced together with the Imaging Transfer Belt (ITB) Unit to get the best printing quality. It is not recommended to change this item only unless the reason for this purchase is your item being physically damaged and the rest of them especially the imaging transfer belt are ok.
Replacing this part is not difficult at all and can be done in official environment. For your convenience, it comes with the detailed instruction manual.