People misunderstand the function of a logo.
a logo is a brand or identity of your business, product and or service. It is supposed to convey the value of your product and set you apart from your competition. It is the most used element in your branding arsenal ( it goes on nearly everything you make or do....) when people say "i'll stake my name on it" that name is usually a logo.
TRUE logo design is a tough biz, because it must not only accomplish everything I mentioned above, but it must be done in a way that survives reproduction in MANY different sizes and media.
So,as a branding professional, I elaborate on when people say "if the logo works". If your brand is working and your logo reproduces well across all media it is actually a BAD idea to to get it redone. remember a good logo should be an INTENSE INVESTMENT OF THOUGHT AND CAPITAL into your brand, which in turn trains your clients to seek out your product or service. if you change your logo simply because its been around for a while ... then that means you have to retrain your clients ( rebuild brand) as well.
WHEN TO CHANGE YOUR LOGO:
1. if you did it wrong in the first place ( did you skimp in getting a logo design? You are paying now by having to tweak or rebuild your brand again in order to represent yourself successfully)
It was done wrong in the second place. It seemed like a bargain, but it was designed for something else. Example that great web logo that was done only in PSD ( so it's low res)or a the idea itself cant be rendered so that print well in B/W, or looks good reduced or enlarged and now that your company needs magazine ads or vans, uniform badges or billboard ads??? At the time you thought.. why pay the extra $$$ when I am never going to get to the point when I need billboards.. but there u are
The non technical reason. YOU change. A logo is tailor made to represent you ( your company or such).. so if you change that logo is no the correct representation of you. 20 years ago I was a goth-teenager.... the logo i made for myself was perfect, now that you are pushing 40... it may actually be detrimental ( that is unless somehow you managed to maintain baby-bat charm in your old age) . But, you see, it not a logo "going stale" but a correction of the company directive.
IBM , for example had the same logo for decades... Coca cola has had 2 logos as far as I have EVER SEEN ( generations).. but they took the time to develop their brand, and they are focused on what they do.
Hopefully this lil rant will help you in your decision. ==:)