The typical forum etiquette is that you not create a thread about something else that's already being discussed on the first few pages or can easily be accessed by a search. (The search functions on some forums work better than others.)

Other than that, there's no real reason to stop yourself from creating a thread as long as what you're posting may be of interest to someone. The amount of data/server use one thread requires is minuscule if it's just small bits of text.