Should I be experimenting more with other ideas?

So, I've done something that I regularly do with briefs. Come up with an idea or theme I'm really keen on using right at the start, and not experimenting with others. I know that some people would tell me that it's better to explore a variety of ideas, but I am really focused on taxidermy because not only does it give me a number of ideas for the content of my book, it is also a subject I'm interested in finding more about and therefore will encourage me to spend a lot of time on.