there are two different things:
ICO period is scheduled since the beginning and it is antecipated to be long (due to market conditions, marketing strategy, etc)
ICO period keeps getting longer and longer and that was not planned since the start... red lights .... these guys are not grabing the investment they want/need, they are greedy, or they are simply scamming for the most possible money... usually these ICOs don't have an happy ending...
cheers