Fueling & Injection - When should I replace stock injectors?

My car has ~117K miles on it. At what point do I know if the stock fuel injectors need to be replaced? Thanks.

when you add a cam and heads.

410rwhp through an A4. Then you need some more flow!

Your stock injectors are Bosch design III's, as long as theyre still flowing enough fuel to support your HP level, they will not go bad.

Sending them in for a full cleaning is a good idea tho.

if you are concerned about how old they are w/ that much mileage and car burning down it would be caused by a leakie O-ring at base of injector.

if you ever smell fuel in the engine area it most likely will be a detererated O-ring.

Thanks guys, I appreciate all the responses.