We have some pretty old fireplace inserts. Only one has ever been used so today we had it cleaned and inspected before we start using it ourselves. I don't think it had been used much by the previous owners of our house. Here is a photo of it before the sweeping.
Here is the same chimney after being swept:
I don't see much, if any, difference. But at least it's been checked out and is deemed safe to use. I did smell some soot but that could have been just from them vacuuming the bottom of the fireplace and cleaning out that ash.