Travel to Toronto to renew F1 visa. How long to stay on Toronto?

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Hi all,

I'm hoping to renew my F1 visa in Toronto this June. My current F1 visa expires in July. I'm a citizen of China, but I don't want to travel back to China to renew my visa. I'm a PhD student in the States and according to my I-20, I can study till 2019. I did my undergrad studies in the States too, so I've applied to US visa for roughly 5 - 6 times, all went through with no problem.

Recap -
- citizen of China
- PhD student in US till 2019
- "good record" (applied for F1 visa 5 - 6 times, all went well)
- I have never applied for a US visa in Canada before.
- I do have a Canadian tourist visa that lasts till 2018.
- According to the US gov website, the processing days for Toronto is 2 work days. <http://travel.state.gov/contenthttps://www.immihelp.com/usa-visas/english/general/wait-times.html/>

I'm wondering if anyone (in similar situation or not) has applied for a F1 visa in Canada before, and if so, how many days did that take you guys starting from the interview till getting your passport back, assuming everything goes smoothly.

Ideally I can book my accommodation and flight in advance, so I'd like to know how many days I should plan my trip to be.

Thanks a bunch!