When I started with SQL Server, I worked on OS/2 and SQL Server 4.2. Eventually I moved on to SQL Server 6.5 at a few places, one of which had heavy workloads. While I liked v6.5 much more than v4.2, there were issues with nested views, and certainly issues with heavy tempdb loads. In fact, at one job, I banned temp tables unless we had no other way to get queries to work. This helped stabilize some of our code, and we essentially had a review group that a developer had to convince to allow temp tables since there were situations where we needed them.
I was reminded of this recently after Grant published his Best Practices and Band Plans editorial. There was this comment, which noted: " I have talked to some people that state "our best practices is to never use..." because they tried it when it was first introduced in SQL Server 2005 and it didn't work for them so now they won't use it at all. "
I've encountered this in my career, and I've been guilty of it. It took me a few versions, and more complex code, to start thinking in terms of temp tables at times. I still try to avoid them, but I'm not afraid of them, and I know SQL Server handles tempdb loads better with each version. They are a tool I reach for sooner, but not immediately. I still try to get a simpler T-SQL query if I can.
Many developers and DBAs have plenty of experience with T-SQL, but how often do they update their knowledge? How many people question that the way they first think to solve a particular problem is the best way? The T-SQL language has grown and changed across versions. Some language changes are great, like the OVER() clause for window functions. Some might not be so great (STRING_SPLIT among them) or have limitations that you might not expect. Without questioning the way you write code and periodically looking for new techniques, you might not be aware that the amazing code you wrote a few years ago could be better structured today.
There is a balance between relying on your knowledge and trying new things. Certainly most of the time I'd expect a developer to write code based on their experience and what works well, but I do think that you also need to periodically investigate new techniques. Regular learning is part of what we hope to help you with at SQLServerCentral, with articles, the Question of the Day, and blogs in our daily newsletter. Maybe you don't read every article, but go through one once every week or two. Whether it's something you do every day or have never tried, you might be surprised what you learn.