EMD - What is too long for a high search EMD

Im looking to build some micro niche blogs but I was wondering what is to long for an EMD? Is there such a thing?

Example: if "reallycheaphomerentalsinpuertorico" got 15K montlhy searches with low volume, would it be worth registering a domain like this?

This is an interesting questions dude... I have a great deal of SEO experience and to be I honest, I don't even know the answer to this... I mean in theory it should be okay to get this domain but Google has also curbed long tail keyword rankings to a certain extent...so it's a tricky one... hmmm I think at the end of the day it's a relativity small investment to buy the domain and if it doesn't carry any weight with ur ranking then it's still cool bcos it was a small investment.. BUT if it does still effect ur ranking then it was a small investment with a huge benefit... basically what I'm saying is if it was up to me I would still buy the domain anyway due to it being a small investment.

with the recent updates google is just trying to tell you stop buying such EMD's....build a quality site no matter what the domain is

It's a big mistake dude.