Reserved instances can help save 70% or higher on your instance costs (versus using on-demand instances). You have the flexibility to pay all, part or nothing as upfront fee, and they are available for 1 year or 3 years' duration at much lower hourly rates. You can also modify or sell your reserved instances, if your requirements change, subsequently. Typical breakeven on these instances vary between 5 months and 7 months depending on the duration of the contract.
Typically, you would run your systems for 3 to 4 months to understand your workloads, and tune and optimize your instances types, OS, tenancy, and so on before switching to Reserved Instances. As soon as you know your instance type and size, try to swap ...
