In the past, BN would only close stores when the lease is due to expire. So, when any given store is underperforming and due for a renewal of the lease, then it will probably close. As leases are signed all throughout the year, it's impossible to say when store closings are going to happen.
Also, the company will sometimes leverage individual markets and economic conditions to sometimes sign a year-to-year lease, assuming they can lean on the landlord hard enough to get a better (lower) rent. There are also kickbacks involved, depending on the local landlord and how the NYC real estate bulls were able to beat them up. If, for instance, a store is in a failing mall where one or more of the anchors has vacated, the landlord will either rebate (of forgive) part of the rent; this, is some cases, will make an underperforming store still profitable--because the biggest non-controllable expense is usually the rent.
Naturally, this matters little if BN gets into a position where it can no longer pay the rents for its hundreds of stores. When this happens, it's game over.
Thought that @YIxDu1u-1txn wrote a good post that shines a good light on the situation.