Most T&M billing is done net 30 days. Most are either sending statements or calling, just like your normal household bills, lights, heat etc.
I've defered, but only as arranged. I've made a percentage/time deal with some who have a real estate deal cooking.
I've purposely walked into a full business and audibly slapped a bill down on the front counter. ( particularly effective after a muddy cobwebbed job)
Nothing works as well as publicly embarassing someone, people hate it!
Loudly proclaiming that they "Are taking the food out of my childrens mouths"
with bill in hand is not at all illegal ,
(It does not slander them..) and will instantly gain a response from any in earshot, if only having them squirm .
A fella's gotta have some fun....