If you want it processed within Canada (by Ottawa), then you should change the address at once. It takes at least 2 weeks to update in E-Cas. Note that,
changing the address won't guarantee that his file won't be transferred to any other LVO.
In my case, my mom is mostly here with me in Canada on Super Visa. I will extend her SV at the end of this year. I was in same boat as you since I was confused too if I should change my mom's address to Canada. At last, I changed it at end of May and got my SA email on Jun 3. Her file was transferred to Singapore and her address was changed few days later in E-Cas. :