Missing longterm deadlines is to some degree understandable as...

Missing longterm deadlines is to some degree understandable as there may be factors that may not be reasonably known at the time (although a good management would do their homework to reduce that).

I have found THE NUMBER 1 DETRIMENTAL effect on SP is missing announced deadlines SPECIALLY SHORT deadlines as it suggests the management does not have a grasp of what is happenING there and then. It results in SH losing trust in the managements credibility. Once that trust is lost, often a positive announcement falls on deaf ears.