How long before departure can an IFR clearance be copied? When flying IFR under the FAA the departure procedure starts with copying an IFR clearance from ATC.

My question is, how long before departure is it okay to go ahead and copy down the clearance?

Sometimes clearances include void times. The context of my question is for clearances delivered, for example, be clearance delivery at a towered airport. These clearances don't include void times. What't the time limit on these clearances?
You can generally get your clearance 30 minutes prior to the departure time you listed on your flight plan.  If you call clearance delivery prior to that they likely won't have it and will tell you to call back 30 minutes prior to departure.