If you don't have blood sample then it gives you enough time to prepare for Extraction procedure. Once you have your sample go for the extraction first then it can be stored for longer time as DNA in blood tends to degrade over time. You can recover it from a well stored 10 days old sample. How can you compare it with the fresh one? The more the storage time, more will be degradation. 

mr sanaullah sajid, Thanks a lot

The maximum time depend on the type of blood sample you are running i.e. what you are analyzing  for .

Hi

about your subject " maximum period of time which the blood sample still fresh and can be used for the RNA extraction".

this is depends on your purpose.

But DNA extraction

"between 2-20 C for less than 4 month"

thank u mr. manzoori

With freezing, It's up to six months

Dear

I think the blood samples not still fresh after storing. For RNA extraction, blood samples can be stored at -20 or -80 for less than 4-6 months.

Regards

mr hussain & Al-sa'aidi, thanks for your comments