AWS reserved instances are buying hours. If you can commit to running a particular instance type for ~720 hours every month for a year or 3, then it makes sense

AWS reserved instances are buying hours. If you can commit to running a particular instance type for ~720 hours every month for a year or 3, then it makes sense to go RI. You don't have to use for one machine running 24x7, you can burst with loads - 2 machines 12x7, etc etc.