Many of us here are 40+, and many started escorting later in life. Some men will pay good money for a mature woman with life experience similar to his own. It's somewhat of a myth that all men want 20-something escorts. The market is big enough for everyone, and being older is most certainly not a hinderance to making good money.
As KBP states, it's about marketing, advertising, services, knowing your clients, area, getting your pricing right. It is also down to attitude too. The advantage of being in one's 40s is that you are less likely to tolerate any nonsense.