CCL:G: Gaussian - memory allocations

Dear all
My question is on memory allocation for Gaussian B3LYP method. Can I determine before the calculation the right memory allocation of a particular molecule. Many articles on the web specify memory allocation can be determined from "NReg" in the output. I have try them for many molecules especially diatomics and it really works. However, the "Nreg" does not appear for many molecules of more than 4 atoms even when I increase the memory capacity.
I have to perform calculations for more than 100 molecules. Can I determine approximately the amount of time such calculations will take.

Thanking you all

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