Well if a treatment is showing results, then continuing may be able to do the trick. Some protocols like ICU call for a few days or week or two of albendazole then a 1 week break, then repeat as needed.
Some gi doctors don't mind giving colonoscopies. Can always mention gastro issues that aren't resolved or answered by anything. Also colonoscopies make doctors money who do them. Question also is if it will pick up the problem, which can be different for different people.
Before colonscopies some places give stuff to clean out the body so some say that may make bugs go into hiding so it may vary for people.