Recent issues with the LLU gateway

[#1]

From the service status messages over the last two days I notice that LLU users were all switched over to a backup gateway due to some kind of failure.
Then there's another message saying that we're all going to be disconnected again to switch us back to the original gateway.
Is there some technical reason that we have to be shunted back to the original gateway, or is it just preferable for maintenance or monitoring purposes?
BTW, idle curiosity is fuelling my question!

[#2]

The secondary LLU gateway is actually shared by some of our IPStream customers, so we tend to keep them separate as it's easier to manage. Also there have been a few speed complaints since we moved customers onto the secondary gateway, so switching back to the original should hopefully resolve these.

[#3]

Thanks Chris;  I knew there had to be a reason!