Most fuel injectors will last the life of the car they are installed in. There are exceptions to this but for the most part your injectors only problem is going to be gunk!
There are three parts on the injectors that will get dirty and cause problems. The first is the filter. As the filter gets restrictive it will limit the amount of fuel flow into the injector. Some of the latter systems don't have a return line in the system so any dirt that gets past the filter is going to stay in the rail and end up in the injector filter.
The next part is the director plate. Old style injectors had a pintle that was used to form the spray patten and flow rate. The new injectors have a plate welded to the end of the injector that is drilled to form the proper spray patten and flow rate. When the discharge holes get dirty it upsets spray pattern formation and volume.
Lastly there is the pintle shaft inside the injector. Too much fuel varnish on this shaft will cause it to drag and slows down opening times which decreases the effective pulse width causing a lean condition. The solution to all three of these dirt caused issues is a good deep ultrasonic cleaning and flow test to verify the proper operation and flow. To get your injectors serviced just visit http://www.mrinjector.us