Jonny,
In fact the delay is only 15 min.
There are also other ways of dealing with this issue, but they all involve leaving your computer on, or at least turning it on before the open.
You can use something like TWSStart and the task scheduler to start up IB and Sierra before the open so you don't miss any data. If you want you can write a batch file that will copy the MT/Sierra files to the IB installation of Sierra (and rename them so the codes match) and run that before the open too, so you don't need to have IB running to the close if you don't want to.