About Trends

The other day, I was talking to someone about what to write next. He told me that I should consider putting my vampire idea on a backburner for now, because while vampire books have been pretty popular for the last couple years, the trend might be over by the time my book would come out. Which is a pretty valid point, on the one hand. Of course you should be aware of trends as you write and submit. On the other hand, however, I don't think that anyone should let trends dictate what they write, or when they write it. Writing a good, tight book with accessible characters and good pacing is way more important than what the trend is. If your book is amazing, it'll sell even if the trend is on the wane.
Any thoughts on this, anyone? Pro- or anti-trend?
An aside, specifically about the vampire trend: Vampires have been popular for a long time. Bram Stoker's Dracula, anyone? So I wouldn't worry too much about vamps ever becoming really unpopular. They've stood the test of time, I think!