I have been in some forums where this happens to be an issues for some of the forum moderators where they don't like it that I brought back to life a thread that's abandoned for 4 years. I have no problems with that as long as the topic haven't served its purpose and if that's the case, I would lock the thread to prevent further comments on it. Whether a topic is too old, as long as discussion can be carried out on it to enlighten it further, it's completely okay by me.