I had sigmoid region cancer in colon . ihad surgery d and took chemo and last 7 years i am gettig colonoscopy done is normal. should i continue colon?

Yes. : It's wise to keep doing this and even recommended as polyps can always develop and give rise to recurrent cancer.

For general: Population, once a decade is adequate. I do not know the features of your sigmoid cancer, but the fact that you had chemo suggests either nodes or a deeply penetrating lesion. I'd listen and follow the advice of your surgeon, and ask if he/she focuses on proctology and if there is one in your community. Total colon scopes are usually done by medical GI folks.

Yes for sure: Need to keep close eye on chance of recurrence. May b able to have them less frequently but ask surgeon.