Chimney cleaning logs do work somewhat to help keep the chimney clean and get rid of some of the creosote.
But you still need to have your chimney swept at least once per year or sweep the chimney yourself once per year to get rid of the creosote completely.
I use a chimney sweeping log once per year to help control the creosote problem and then still I sweep the chimney at the end of the burning season.
Also make sure you use good dry seasoned firewood in your fireplace or wood burning stove to prevent creosote buildup in your chimney.
The wood that is not dry or seasoned enough will create more creosote and cause a potential chimney fire plus the non seasoned wood will not burn as hot as dry seasoned wood.
Most firewood needs between 6 months to a year to season and be ready to burn and for oak firewood it usually needs 2 years to 4 years to season properly.