Now in my sixties and still CF. In my thirties the only real down side was the loss (largely) of friends who had chosen to have children so could now no longer come out to play.
With spare money/disposable income. Want to go on holiday? we do. Want a lie in at the weekend? we can. Peace and quiet? lots. None of this possible with kids as they take over your whole life.
This is what I enjoy most about being CF, everything in life is much more flexible. Both my partner and myself are working shifts and our planning doesn't depend on weekend and school holidays. Going out for a nice dinner on a Tuesday is much more enjoyable when the restaurants aren't full. Also, traveling after the summer rush is what we prefer. Things are somewhat cheaper, popular areas are emptier, and the weather is cooler.
Currently in my mid 30s. Life is good. Spent the past year trying to turn over a new page in the book of life. Hoping to emigrate with my partner soon. I've already changed to a remote working job. I split my spare time between: running, photography, sailing, hiking, coding & gaming. Lots of this would be impossible or very difficult with children.
Being CF had allowed me to make choices that would have otherwise been unavailable to me.
I change careers when I want, move where and when I want. I'm open to peruse, or end, relationships based only on my goals and needs.
As others have mentioned, dealing with friends when they have families can be an issue, but honestly, I haven't had too much trouble. The one couple I'm close with that has kids still find time to do things, and I'm someone they call when they want a night away to do things.
Not once have I felt regret, but I'm from a large family, and have many nieces and nephews, so no one looks at me to "continue the family name". In fact, being the black sheep, there is often a sigh of relief.
Dating can be a challenge, I've had more than one relationship end because they wanted kids, and I've had some never start because they had kids already.
Now I'm with someone who is as CF as I am, and this only ever comes up in jokes.