This has been troubling me for some time, and I'd really appreciate the input of other professionals.

Short background: I started programming when my parents bought me my first computer in 1988 (at age 14, I'm 39 now). I followed a couple of other career paths before finally becoming a professional programmer in 1997. Late bloomer, perhaps, but that's how it was. I'm still happy with my choice, I love programming, and I consider myself good at what I do.

Lately, I've been noticing that the more experience I gain, the longer it takes me to complete projects, or certain tasks in a project. I'm not going senile yet. It's just that I've seen so many different ways in which things can go wrong. And the potential pitfalls and gotchas that I know about and remember are just getting more and more.

Trivial example: it used to be just "okay, write a file here". Now I'm worrying about permissions, locking, concurrency, atomic operations, indirection/frameworks, different file systems, number of files in a directory, predictable temp file names, the quality of randomness in my PRNG, power shortages in the middle of any operation, an understandable API for what I'm doing, proper documentation, etc etc etc.

In short, the problems have long since moved from "how do I do this" to "what's the best/safest way of doing it".

The upshot is that it takes me longer to finish a project than a novice. My version may be rock solid, and as impenetrable as I know how to make it, but it takes longer. 

The "create file" example above was just that, an example. Real tasks are obviously more complex, but less suited for a generic question like this one. I hope you understand where I'm going with this. I have no problem coming up with efficient algorithms, I love math, I enjoy complex subjects, I have no difficulties with concentration. I think I do have a problem with experience, and consequently with a fear of errors (intrinsic or extrinsic).

I spend almost two hours a day reading up on new developments, new techniques, languages, platforms, security vulnerabilities, and so on. The conundrum is that the more knowledge I gain, the slower I am in completing projects.

How do you deal with this?

You're not any slower in completing projects. Previously, you thought your novice projects were done when they really were not. You should sell this quality to clients.

"This company might get it done faster and cheaper, but is it really done? Or will you be hunting bugs for years?"

Beyond that, you need to know and accept the old idiom: "Perfect is the enemy of good."
