I hear from many restaurants of all sizes whose owners are managing decline. Normally it’s too late to help them because they’ve run out of capital.
The best way to avoid this problem is with foresight when you’re a success and making money. If you’ve waited for regular customers to stop coming you’ve left it too late and you may get sucked into a whirlpool from which there’s no escape.
I think this is worth repeating, staying clear of the downward spiral before it gets expensive and difficult is far better than paying a premium in a rush when it becomes an emergency and your money's all spent.
Good design; kept up to date, is a cheap, highly leveraged way to retain your customers and attract even more. The cost of a refurbishment and re-brand that will last a decade or more is normally less than the value of 6 months’ of sales for a successful restaurant and a tiny fraction of the cost paying its staff and rent over its lifetime. What's more it nearly always pays for itself with renewed customer engagement.
The magic of slack (surplus profit or capital or a little extra time in the refurbishment process) is that it gives you the resources to stop and avoid problems or fix them when they’re small.
Over-optimized and fast-growing restaurant chains often misunderstand the value this slack, they always wait until something is a pressing emergency, because their owners don't have a moment to spare. Expensive.
Careful design now is almost always cheaper now than rushed design later.