What you could do is get enough letters from home program so that you're covered, and then if your letters from aways come in later you can substitute them in.

Also, letters aren't important only for getting interviews, when you go on your interviews many interviewers will peruse your letters in front of you. If you get a really good letter in late October or even November, I wouldn't hesitate to substitute it in then. It might not help you get more interviews by then but could help you make a better impression in the interviews you do have. And for those programs that don't send out interview offers till December, chances are they are waiting until November to read the applications, so it might help you get interviews there.

agree mostly with what was written above, BUT substituting LORs on ERAS doesn't work as it sounds. once you submit a LOR to a program on ERAS AND the program downloads it (which usually is very soon after submission in my experience) THAT LOR will not get replaced by another that you substitute at a later time. if you think your letters will get substituted (as I did) you will find that you may have more than just "3" or "4" (as required by specific programs), in your file at a later time and this may put off certain programs- if you have 5 LORs sitting in your application on Nov 1 and the program only wants 3 you may get eliminated from interview prospect list.

So to add to what was written, I would not submit a letter just to hold a spot on the application, even if you know you intend to submit a LOR at a later time. if you intend to submit a future letter, I'd say wait to do that once its in your ERAS account and only then submit it.

It does not sound like when you are going to do the aways, that they would be helpful, esp for letters. The letters submitted in the beginning count. When programs state they want three letters, they will look at those three.

yup.. that's how it works