Can't relate. Since our house was built in 1880, there was no such thing as ducts. However, we have lived in more modern structures that DID have ducts. Never had them cleaned because we didn't live in them very long.
All I can recommend is that you do your homework, especially checking out the integrity of the company you select to do your work. Doing a BBB check is good. Also, if possible, get whatever work is done in writing if there is any type of warranty/guarantee offered by the company.
"As a girl I had zero interest in the stove." - Julia Child
This is real inspiration. Look what Julia became!