I didn't say a regular schedule, you can put things out at consistent intervals, but the amount per update gets less.Improvements in skills, tools, and discipline can offset feature and quality creep. A regular schedule is definitely not an indication that "something is wrong."
Improvements in skills means that you will let less problems slide, you pay more attention to certain details, and so on. If they are not going slower, they are not improving. Some things will be faster, but you will then take more time and care about other things.
It depends, there are some who hit a plateau, and then speed is all they improve, but it depends on what you want to get better at. But any improvement in quality takes time to do, unless you have a ton of money to dump on it.