That gray-out is based entirely upon the last time the client sent a Report. If systems are going into sleep mode/power saving, getting turned off, disconnected from network, or just spending too long evaluating content between reports, the system can become grayed-out.
Whether that has an effect on evaluating new fixlets or processing actions can vary. If it’s just some background evaluation that takes too long between reports, the client can ignore that and give priority to “new” fixlets / actions, executing those & sending a report, before going back to evaluate the long-running things.
Have a look at Tip: Troubleshooting Client Reponsiveness for tips on how to troubleshoot and determine which things the client might be spending too long evaluating. Common issues would be any Analysis or Retrieved Property that descends many folders using the descendant inspectors, or calculates many hashes or large file hashes.