Imagine I have ISP1, managed router1, serving my company. ISP1 advertises let's say my prefix a.b.c.d/16.
Then I want to install another router2, managed by another service provider. That will become my production router, therefore it will also advertise a.b.c.d/16.
Later ISP1 connection and router1 will go away and router disconnected.
Is there any problem to have both ISP's advertising a.b.c.d/16 concurrently for a while? Or should I plan a coordination?
If that is OK, which route would be preferred to get to my company, since both ISP's would be advertising it?