Beside having @Matt looking at this - there's a FAQ too! 
https://docs.mybb.com/1.8/faq/moving-to-a-new-web-host/
I'd only take issue with DNS propagation. Unless you have some control over TTL (Time to Live) settings on your DNS service, and cached DNS records - I'd plan for 2-3 days. Anything quicker is a bonus.
https://docs.mybb.com/1.8/faq/moving-to-a-new-web-host/
I'd only take issue with DNS propagation. Unless you have some control over TTL (Time to Live) settings on your DNS service, and cached DNS records - I'd plan for 2-3 days. Anything quicker is a bonus.