Some poor quality projects often prolong the ICO's time to raise enough capital. But not all ICOs are of poor quality, depending on the purpose and timing of the project management team. I like to invest in ICO projects for about 2 months.
This is true there have been some projects that have reached the hard cap in a matter of minutes and when that happens people begin to complain about the fact that they did not got a chance to invest in that project, so it makes sense for icos to have very long periods to try to get the necessary investment so people do not complain about it afterwards.
If many investors are interested then all tokens will be exhausted sold with a very short time..
if ico duration is old but unsuccessful then you do not get anything but if ico long and reach hardcap it gives you chance to get many advantages.