Best practices for Idp Signing certificate - Idp Initiated workflow

What are the best practices for Idp Signing certificate in a multi-SP scenario ?
Is it required to have a different signing certificate for each SP ?

There’s no need for the IdP to have a different certificate for each partner SP.
The primary disadvantage is that there are multiple certificates to manage.
We do offer this support but the typical use case is to support staggered certificate roll over.
We recommend using a single certificate.