If you have a business requirement which has a need to retain database backups for longer than 35 days, then you have an option to use long-term backup retention. This feature utilises the Azure Recovery Services Vault where you can store up to 10 years’ worth of backups for up to 1000 databases per vault and 25 vaults per subscription.
There are some guidelines that you need to follow to successful set this up:
Your vault MUST be in the same region, subscription and resource group as your logical SQL Server, if not then you will not be able to set this up.
Register the vault to the server.
Create a protection policy.
Apply the above policy to the databases that require long-term backup retention.
Arun also looks at restoration options.