Originally Posted by
boilerpilot
Never flown 135, nor have I ever studied the regs too much in depth for 135, but once you get hired with a 121 carrier, the written remains valid indefinitely.
It's the same for 135. As long as your continuously employed your written will be valid.
However that doesn't mean that when you go to interview somewhere that they're not going to require you to have your ATP written done within the last 24 months. One of my co-workers just went through this.