I have plenty of nitro fuel such a 10%, 20%, and a 30%. They are in their tanks but they are all open(they are closed but they been open). If i let them static for a long time such a 3-4 months is bad for them? If yes, what i must do to prevent this.!!!

Make sure they're completely airtight and store them where the temperature is reasonably constant which will reduce their ability to "breathe" even if they seem to be airtight. If they're in a translucent plastic container then keep them out of direct sunlight because I've heard it can degrade the nitro. Stored like this then they should still be good in 20 years time .

Ok thanks