Short Answer: Doesn't slow down.
Medium Length Answer: I asked the same question, thinking it was only temporary. It wasn't. Began using these forums at age 2, he's now 4.
Long Answer: I personally just couldn't believe what I was seeing. Thought that of course all children must be doing these things. Went through a long denial period. Then by 2.5, someone looked me right in the face and told me he was gifted and I finally got it. For the next year, I was grieving that my parenthood with him wouldn't be "normal" but challenging and exhausting. At 2 and 3, he became so intense I lost my mind. Now at 4, the learning hasn't 'slowed' down, but it's different and more mellow because he can read, write, spell, and do math (not that your child or any gifted child needs to know these things at four, but for mine, he worked everyday to understand these skills and he is thrilled to express himself and have these tools to work with). He's about 2.5/3 years ahead academically (read a book tonight, I look at the back, it's a second grade level reader, into multiplication among many other topics that he talks about from sun up to sun down).
You'll find your stride as he grows and you grow as his parent.