I have pretty much the same situation as you (the original poster), same amount of years, the same feelings, and the same assumption that quitting would be a big mistake, at least financially.
Try to resist all those who say you should follow your heart and jump off the wheel, because there’s a good chance it might actually be a big mistake.
However, don’t also turn a blind eye at these feelings you’re having. If you’re bored, you are bored.
One thing I’ve found very useful is to constantly keep a few alternative plans in the drawer. Their mere existence reduces the feeling of being trapped by one’s career. They are also a security warranty. If my job was suddenly to end, I’d have something else to go on with, and not starting from scratch.
Hobbies are also very useful. Writing is such a hobby for me, and there are a few others. Writing is certainly something I’d love to do all days, but since it doesn’t pay the bills, it’s better to convince myself that I need to do one thing for income so I can then sit down in a comfortable flat to type my unprofitable manuscripts and poems.
I know, time is a major constraint here. But one can utilize a lot of good time from other wasted moments than a paid job. For example, I quit both TV and computer games long ago for the reason that they consume time. My free time should always be dedicated to what I truly love.