Everything I've read indicates that bad by default is the way to bet.
Small companies routinely think one big customer will have them set for life. They will have it made in the shade.
It seems to be the small business version of the "winning the lottery" fantasy.
And most of the time, you become their bitch. They make demands, you have no real choice but to meet them because it's such a big chunk of your revenue that you can no longer make payroll without them.
Rule of thumb: Don't let one client be more than 20 percent of your income if you want to actually remain an independent business and not get pwned by these people.
They are unlikely to worry about your welfare and you can get into financial hot water if they come up short financially and decide to stiff you.
They likely have a legal department or lawyer on retainer who has told them just how much they can legally shaft you and it can threaten to put you out of business.
Sometimes small businesses who survived such incidents change their stated policies in defense after nearly going under.