Targets usually fall into two categories: those set by the board in line with its strategy for the management and development of the organisation, and those for the board itself.
In the first category, timelines can be set, and you should ask for an explanation of why any deadlines are missed. In these difficult times especially, this is likely to happen - but it is acceptable if reasons are stated clearly and plans are put in place for how targets will be achieved in future.
Flexibility is key. The board should accept that changing circumstances might mean targets are not achievable after all. But any failure to meet them must be reported transparently, and the board should support staff in whatever they are doing to resolve the situation.
Some board members see their own targets as aspirational rather than achievable. But if this is the case, why waste time setting them? Effective boards are good at blue-sky thinking, which often helps their organisations to achieve amazing results. But targets must still be measured against sensible and well-researched objectives, with clear deadlines for their achievement.