Say like you have an idea that says: 'X is a cheap alternative to Y' (Smith 2010, p. 2). Now you write a paper about ABC and paraphrase Smith's idea. Next week, you write another paper which happens to have an idea similar to ABC and you had to use Smith's idea again to solidify your choice or analysis. The same thing happens for a third time, etc... Can you use it again over and over? Albeit I will admit that I try to differently paraphrase the idea each time I use it.