Prior year return efile signature date

[NECPA in NEBRASKA]

I read the rules on stockpiling, but I just want confirmation that I read them correctly. I have a bunch of prior year 1040's that I am wrapping up. May I have the clients sign the 8879 now and transmit them when efile opens in January or do I have to wait to give them to the clients so that I am not stockpiling? I believe that it's not stockpiling if the IRS isn't open for efile yet. I just do not want to paper file all of these returns. One of the clients needs them right now for a loan.

Thanks!