Thank you,
bitflipper. I didn't know that about songs you send out for mastering, so that information will come in handy some day, I hope.
The songs I'm doing are ones I am trying to master myself (hahahahaha

), so I'll try to judge how much time is appropriate.
Nodding in recognition of your experience of leaving/not leaving enough time at the beginning! I think my dreams of coming up with a great and long introduction and so leaving 24 measures available are grandiose, but I'm always afraid I'll be stuck with too few!
Thanks again,
LJ