A friend of mine was over 40 when he learnt to fly, instructed for three years during which time he also did some charter work on a twin, then with something over 1500 hours got his first airline job at around 46 and now seems to be heading towards a command. I also know another ex instructor who had been instructing for about 8 years and recently went to a major airline for his first jet job aged 42. He also did some charter work before the airline job came up, so there are people who do it later in life.