A CTO is in effect for six months and may be renewed any time before its expiry. A CTO can be renewed for a period of six months. There is no limit to the number of times a CTO can be renewed.Being on a CTO means that you must follow the treatment and care requirements listed in the CTO. CTO is in effect for six months and may be renewed any time before its expiry. A CTO can be renewed for a period of six months. There is no limit to the number of times a CTO can be renewed.