Never too old
Thought i would give a story that might give anyone out there a little hope, who may think they are too old.
I'm currently doing my cpl training and have an instructor with an interesting story. He like many people was doing a **** boring job for many years, and then at the ripe age of 37, gave it all up and started his flight training. He got his first job at 39, flying charter in 206's and then went way up north to papua new guinea and flew twin otters around up there, and built heaps of hours (sounded a little crazy, but most definatly worth it).
From there he went where the work was, the uk, central europe and asia, flying some amazing aircraft and getting what I think was pretty good pay. Only about 5 years after starting he cracked his first airline job, flying jets out of sinagapore.
Basically to cut a long story short, he then got a job with Cathy and flew the 747-400 for 16 years, in the LHS for about 10 of them. He was 45 when he started at cathy!!!
So honestly, its never too late. As long as you are prepared to go where the work is, and take that step outside your comfort zone.
If you really want to be in LHS of a jet for a major airline, there is nothing stopping you, no matter how old you are.
Cheers and safe flying