Great thread!
I will chime in here.
My shops have been open for nearly 24 years and we're still at it. Business is very good and has been for the past 4-5 years. I've learned a lot from my mistakes and am still constantly learning.
There are myriad, obvious reasons that stores don't succeed,like location, insufficient capital, macro-economic, inventory issues, personality problems, etc.
However, I've observed one major reason that most stores fail:
The new owners bring tons of passion, but have NO experience buying and selling stuff.
Before committing to a full time brick and mortar, and all that it entails in cost and time, I would buy and sell part time for as long as possible, either at conventions, ebay, facebook groups, etc.
This experience and knowledge of actually having to buy and sell correctly and manage that bankroll is something that is best learned by doing. And, is best learned on a small scale so your mistakes don't bury you.
I have seen many, many shops that had plenty of capital and plenty of passion, but zero expertise in running a business where you have to buy and sell correctly. They run into trouble fairly quickly. I would also highly recommend doing that road trip suggested earlier and get as many ideas from other shops as possible.