Reports show the Duraflame logs and similar packaged logs found in stores are easy to use but are extremely expensive when used solely and also not safe when used over a long period of time. They do burn hot whixh is good however they are actually sawdust and held together with wax or paraffin. It is the latter part that is the problem. They will soot up the chimney badly in just a short time. You can go much longer between cleanings by burning wood for which fireplaces were made to burn. Sweeps have recommend cleaning chimneys on a monthly basis when using the packaged logs exclusively.
It is perfectly acceptable to cut or tear off small pieces of the logs to start your fires. The ill effects of the log will be minimized by the compliment of wood that the starter is used to ignite. Otherwise use the logs sparingly and save your pocketbook and chimney.
I read on line one person said they were fine for burning as long as you burn a Chimney Sweeping Log to handle the creosote buildup. They are not fine to burn and the Chimney Sweeping Log does nothing to ordinary creosote which is found in 95% of the chimneys we do. It only works on 3rd degree creosote which is rarely found in chimneys and even then its effect is minimal. Our concentrated reactors work quicker and better in attacking this problem.