The trouble is, once you start learning a technology, to get proficient in it you have to dedicate a lot of time to understand all it's cleaver functions and more than usually it quirks. I find that I start to forget what I knew previously. Not only that, technology is always moving forward as are new tricks so by learning something else at a lower level you are losing time that you would be using to learn the new tricks of the old technology. I definitely go for that 'jack of all trades and master of none'.
I moved away from notes development in the commercial world to become a business analyst but I love lotes and still dabble at home. I'm still learning though now I'm often relearning. The reason I moved to being a BA was actually to get away from the constant need to learn and to stay on top of the tree but domino development is still in me. Having said that, you have to know a number of languages to be a top notes developer (and I know nothing about Java nor had the time to learn). Moving to .NET was something I just wasn't willing to do especially as I had tried and thought it was a complete nightmare compared to developing in the notes enivironment.
I suspect you are getting to that point where job security is on your mind and want to branch out. That's what I got to and thought it far safer to just leave the development industry.