Infrequent deployments don't prevent on-call scenarios. Stuff can and does still break between deployments, as external dependencies change, load increases or it's characteristics change, "time bomb" bugs go off, or any of a huge number of other things happen. Infrequent deployments mean that responding to these events is slower and more costly.
Infrequent deployments also greatly increase the risk of problems during deployment, because infrequently exercised pieces of code (i.e. The deployment code/scripts) are more likely to be buggy, and because gobs of changes pile up between deployments.
With that said, continuous deployment probably should not be happening at night or on the weekends unless you have rock-solid automatic rollback and the necessary monitoring to trigger it.
Infrequent deployments also greatly increase the risk of problems during deployment, because infrequently exercised pieces of code (i.e. The deployment code/scripts) are more likely to be buggy, and because gobs of changes pile up between deployments.
With that said, continuous deployment probably should not be happening at night or on the weekends unless you have rock-solid automatic rollback and the necessary monitoring to trigger it.