Would it be possible to archive data back to on-premise once the data retention limit is hit - specifically with logs?
Maybe a powershell do download everything.
It would be handy for organisations that need to keep information longer than 12 months.
In the future we will work on plans for higher retention policy.
For the ‘export’ functionality, you might want to check the API idea http://feedback.azure.com/forums/267889-azure-operational-insights/suggestions/6519057-programmatically-submit-search-requests-and-receiv but, realistically, after you uploaded terabytes of data over a few months time… even the concept of downloading everything back at that point seems daunting.
The whole point is that SCOM databases have always been the bottleneck to scalability for scenarios with large volume of data. OpInsights is a new backend that is being designed and evolved specifically to deal with those. We take advantage of Azure's elastic services for this, and we are not at a point where we can 'freeze' and 'package' this technology for on-prem use. Maybe in the future as the architecture stabilizes.
Another idea would be is possible for the Ops Insights Agent / SCOM agent to first put the logs on a onpremise server before shipping them up to Azure. Means there is always long term on-premise copies for archival purposes.