Oil change

[bigbootch]

I understand that you're supposed to get your oil changed after X miles, where X depends on a number of factors and who you ask - but generally between 3k and 10k miles. My question is, is there a similar "time limit" for you engine oil? Specifically, say you have a car (standard $25k car, not an exotic or anything) that you drive 600 miles per month, when should you get your oil changed? It would take 5 months to hit 3k miles, and 8 months to hit 5k miles...