F**k You. Pay Me (2011) [video]
vimeo.com
vimeo.com
Size doesn't matter. Small clients believe they are entitled to such childishness. Large clients just don't care and will use their size to bully you.
When in doubt (and this should be your default), get paid weekly, every two weeks at the most. If it's monthly, negotiate a higher rate to try to hedge your risk a bit. Four weeks is nearly 10% of the year. Being denied 10% of your revenue is going to hurt. If you think "Ms/Mr X at Company Y would never do that." Ha! Think again.
Useful information for folks that hang their own shingle.