Fuel injector issues

[crr31c]

Ok so #4 injector stuck open and #6 stuck closed on my 05 Expy 104,000 miles. Ford dealer replaced both injectors under 07m08 program, and no engine damadge luckily. But I am just a few months away from being out of this extended warranty. And they only replaced the 2 injectors that failed. So here is my question. Is there a new model fuel injector out there? I would like to just upgrade all 8 injectors myself with a better injector not prone to failure. I got lucky this time and didn't trash engine. I would like to nip this in the bud before it happens again, but I can't find any info on an improved injector to install. I asked service guy what causes the failure on the OE injectors. So I could look for an upgrade. He could not answer me. Any help would be great.