I think it is perfectly fine to update a review. But not because a person's opinion of the game has changed based on time. If it's just a time issue then it could be because other games that the reviewer feels are better can alter his review/opinion unfairly. However, when a game patches itself I think the reviewer has an obligation to update his review, as things that could stop someone from purchasing the title may have been addressed. Though I feel the original review should stay, just have a small update and revised review score at the bottom.