I am not sure that age by itself is going to be the main reason. I think it is going to have more to do with the circle of people a person communicates most with.
I have been texting for 2-3 years. My husband, really only for about 2. I am 45, so is he. My mom texts, but she PREFERS talking. She is 72. My Dad (also 72, next month) doesn't text at all... but they share a cell phone and she uses it and he really doesn't.
How did I get started texting? My SIL and BIL (husband's brother and his sister) would text me from time to time. SIL is almost 10 years younger and has been a cell phone cutting edge user for a long time. She is part of the group of people that got rid of her land line and only used cell phones early on. And upgrades every time she can. All her friends are the same way. BIL teaches at a tech school, and all of his students are younger and text. And he was constantly in communication with a cousin who is extremely tech oriented. So those 2 would text me whenever we were in town visiting, b/c it was easier to say "We are upstairs in the book store whenever you get here." when we were trying to rendezvous than to try to call us when we were trying to park the car. We could see it after we parked, rather than while potentially fighting with traffic.
Then my brother started doing the same when he came down here to visit. He turned 50 a few days ago. He has 3 teen daughters. So, 5 smartphones in their house, and you can bet it is much easier as a parent to teen girls to keep up with them if you text.
My other brother, he rarely does phones or texts. But his wife (who is mid 30s) texts freely.
I also text freely with a friend of mine (who is 51) rather than talk, except when we are in person. She will keep you on the telephone for an hour, but I can text her and say "what time are we meeting?" and be done. Where if I'd called, I'd still be on the phone with her as we pulled into the parking lot simultaneously. Her husband is like mine and doesn't use much tech. He will call, sometimes. But rarely uses his phone, and certainly not to text. They have 3 kids, all grown, who are big texters.
My husband started texting more when the younger guys he works with started communicating with him that way (setting up golf tee times, sending jokes and pictures of restaurant signs, etc). He hated texting when he had a plain flip phone. But now he has my old phone with a QWERTY keyboard and he texts me all the time. Just not EVER while driving.
He does it when I go shopping: "We are out of bananas." "I need beer."
And I do it when he is at work and can't be interrupted (he's an air traffic controller)... "I'm going into town, tell me what you want from ____ (to eat)."
He would never have started texting, except that he had friends who sent him texts. And he hated trying to respond, while he had old technology to do it on. He still doesn't want a smartphone, bc he doesn't want to understand touch technology or figure it out.
I text my kids. Heck, black Friday (Thursday?) my daughter was sending me text/ichats from my ipad of links to clothes/boots she found on amazon that she wanted for Christmas, while I was standing in a line for technology on sale.
Me? I'm a stay at home mom, with access to a landline almost all day, except when I am in the car. But I will text my SIL (who is at work) if I have a question for her, and when she gets a minute and looks at her phone, she'll text me back. I am not disturbing her at work. And she is able to send whatever info it is that only she has.
I also like that I don't have to respond instantly. Everyone knows that texting and driving is a no-no. I just don't even look while I am behind the wheel. If it is something crucially important to deal with, then people call rather than text.
But texting can be fun. And it can be very efficient. And fast.
But my mom is 72 and texts. I am 45 and text. My brother is 50 and texts (almost his sole communication--he never uses a phone to TALK). I don't think it is an age thing at all. But who you deal with who uses the technology.