If you have a masonry fireplace (not a metal pre-fab), doing what you're doing, don't worry about it; once/ decade would be an abundance of caution.

Berlin,

I live in a condo so I'm pretty sure it's the metal pre fab you described. The person who lived here before me Never used it so its doubtful that there is any or much creosote buildup. I did have a chimney sweep done when I first moved here (almost 10 yrs ago). I just hate to waste my money!

Hi,
I can understand your problem.There is important to safe fireplace and energy conservation.Regular firebricks can't tolerate the higher temperatures.you should check chimney cap as regular habit. I Have one question
is it wood burning fireplace or gas fireplace?

With a pre-fab fireplace w/ good cap, have it inspected once every three to five years if occasionally used. With this type of fireplace creosote buildup isn't the main concern, the innermost liner in the triple wall stack is the concern - it's typically NOT made of stainless steel and has been known to rot out prematurely with significant consequence for the safety of the system; you want to make sure that this inner liner is intact and in good condition every few years.

Royalsmith, it is a wood burning fireplace. I only burn the fake firewood when I do use it. I guess it's time to have an inspection on it.
Berlin, how do I know if its a prefab or not? I live in a condo...does that make a difference?