Load thresholds are needed if you deliberately oversubscribe your machines and you need to prevent excessive system load. Suspend thresholds are also used to prevent overloading the system.
Another case where you want to prevent the overloading of a node is when the execution node is still open for interactive load. Interactive load is not under the control of the grid engine system.
A compute farm might be more single-purpose. For example, each CPU at a compute node might be represented by only one queue slot, and no interactive load might be expected at these nodes. In such cases, you can omit load_thresholds.
To disable both thresholds, set load_thresholds to none and suspend_thresholds to none. See Configuring Load and Suspend Thresholds, and the queue_conf(5) man page.