Should be another easy one here, but I need clarification on what they define as "heavy utilization" for Reserved Instance types. From their Website:

Heavy Utilization RIs – Heavy Utilization RIs offer the most absolute savings of any Reserved Instance type. They’re most appropriate for steady-state workloads where you’re willing to commit to always running these instances in exchange for our lowest hourly usage fee. With this RI, you pay a little higher upfront payment than Medium Utilization RIs, a significantly lower hourly usage fee, and you’re charged that lower hourly rate for every hour in the Reserved Instance term you purchase. Using Heavy Utilization RIs, you can save up to 41% for a 1-year term and 58% for a 3-year term vs. running On-Demand Instances. If you’re trying to find a break-even utilization, you’re economically advantaged using Heavy Utilization RIs (vs. On-Demand Instances) if you plan to use your instance more than 43% of a 1-year term or 79% of a 3-year term.

I'm assuming that, if I'm planning on running a 24/7 Web Server, then regardless of how many resources I consume (bandwidth, cpu cycles, memory), I would want to go with a Heavy Utilization Reserved Instance? This one Web Server in particular will likely barely budge the cpu, but it needs to be up and running 24/7.

Not 100% on what they're defining as "heavy".