Family and other responsibilities can take you away from gaming or convert you into a casual gamer. I've been quite a hardcore gamer since I was a kid and it lasted about 20 years... I kinda lost interest in gaming by the horrible years of the end of the last generation of consoles. Turned into a PC Gamer for RTS and things that wouldn't take that much time away from me.
Now I'm back with all 3 platforms but it's indeed pretty hard to keep up with news games so I became more picky. Also, I've played so many games that it's much more difficult for me to be impressed by new titles. Said this, there's been titles that nailed it, like The Witcher 3, Ori, TLOU, God of War so name a few.
If, for some reason, you're not willing to have kids/get married... then you can be a hardcore gamer virtually forever, and best thing is, you most likely will have to money to cover the costs for all the bells and whistles tech can offer. Have many friends in their late 30s and one in his 50s who are.
BTW. If you have kids, you will also need to be careful with what you play and for how long. Gaming can become an addiction, and I've also seen the ugly face of it. Guys in their 30s with low end jobs, living with their parents and spending their money on games.