Yes they wont slow down if all of them are configured to get update at same time ( push mode)
we have few issues with SAN when all of them tried to update at once. what we did was to configure hearbeat as PuLL mode with different interval. 6, 12, 18 hours, this setting was helpful to us.
to bypass the update you can set your cleints to get update from internet using a schedule to a future date like 2016, again its all manual once done you need to enable those manually.