A bad time for new shoes...?

You have time to break in a new pair, but it probably isn't necessary, unless you think that these are already borderline.  Unless they have taken an unusually hard pounding, they should last.

You probably know this but in case not:  It's probably not a good idea to break the new shoes in on a 20-miler, especially if they are shoes you haven't tried before.

New shoes don't need to be broken in these days, they're good right out of the box. If your shoes were worn (questionable at 260 miles) and you were going to the same make and model now would be a great time to switch.

However...

If you're contemplating switching shoes it's not a great time as your feet and joints may need time to get adjusted to a different time of shoe.

Question: if you chose your current shoes "out of comfort," and are having no problems with them now, why would you contemplate changing? Is there another consideration besides "comfort"?

Right.  She said she was likely switching shoes.  What I meant by 'breaking in' (OK, bad old timer language, I agree) was getting the feet used to the shoes, not vice versa.  Thanks for correcting me.

I personally would not change out shoe models within a marathon plan.  I have had good success with sticking with the same model and just replacing them at 350-ish miles.  But of course your mileage will vary.

While "breaking in" is not required on shoes anymore, I still like to log at least one longish run and a faster run on a new pair before racing in them.

If you start with a new pair, wear them for a couple of your shorter runs and save your current shoes for the long run and race. 

I usually start rotating in a new pair when the old pair has 250-300 miles and alternate them for a month or two.