New shoes time approaching, and dilemmas ahead

I have become a fan of these Brooks Glycerin 20 shoes. So much so that I bought two pair of them last year (though the second pair was 40% off).

The pair on the left got me through the marathon earlier this year, and I've been using them for "long" runs since then. I have a pair of Brooks Ghost 14s (which I wore for the Marathon last fall) that I've been using for my shorter runs. It's just about time to retire them.

These Glycerin 20s on the left will still give me plenty of training miles going forward, but I need to start breaking in the ones on the right. I will wear them for the marathon coming up in a few weeks. I actually wore them this morning on an inaugural 6 miler. I will probably wear them on a couple more runs before the marathon... maybe a 12-miler and then a shorter run. I need to make sure there are no "issues" - and I didn't notice any this morning - but I'd like to keep them fairly fresh.

My dilemma: 

I can currently get yet another pair of Glycerin 20s for under $100, and I'm not sure if I should splurge and get a pair for later next year (these two pairs should suffice for quite awhile yet). But, you know, I don't make any money and it's a little hard to justify spending too much on shoes...

However, as I mentioned, my Ghosts are at the end of the line for running, and I'd like to have another pair of them. I went several years running almost exclusively in Ghosts. That is, until last year when I fell in love with the Glycerin. But I like to have two different styles of shoes to alternate during training runs. So I kind of need another pair of Ghosts (unless, of course, I'd find something similar that I wanted to try). But then do I pass on getting the third pair of Glycerin 20s, or totally splurge and get both?

If they didn't change the shoes so much from year to year it wouldn't even be an issue. I'd just get some Ghosts. But they do. That's why I'm still wearing versions from a couple years ago instead of the newer iterations. And the issue is compounded by the fact the Glycerin 20 is a size 8.5 and the Ghost 14 a size 9. Will the newer versions of each fit the same? I don't know. So...

See how hard it is to be me??

Ugh.