Tax question: Can personal biz expenses accumulate over years of no income,then all be deducted when there is?

Tax question: Can personal biz expenses accumulate over years of no income,then all be deducted when there is?
I earn an income from a regular full-time job, but very occasionally (every few years) I also earn additional income as a freelance writer. In the past, I have tax-deducted writing-related business expenses only within the tax years in which I earned writing income. During years where no writing income was generated, I kept records of all writing expenses but did not claim them as deductions. This year (2006), I again will be earning money from my writing, the first writing-related income since 2003. My question: can I deduct not only 2006 writing expenses, but also writing expenses incurred in 2005 and 2004? In other words, are such expenses accumulative, a kind of multi-year loss which can be retroactively deducted once income finally is generated?