One of the main problems with any sort of goal setting technique is that after a lot of effort has been put into designing and shaping goals, people forget them and only remember them when they are due. OKR methodology addresses this problem with constant monitoring.
The progress toward Key Results should be measured weekly to see how much has been done. If a week has passed and you’ve got no progress, there is a problem that should be addressed by the team leader and the person responsible for the goal.