I've been using the 50/50 payment system for my web design clients (50% upon signing the agreement and 50% prior to launch). However, I am giving some thought to requiring 100% upfront because I often finish projects early and have to wait even longer (past the quoted completion date) as the client gives reasons for why it will take "a few days" to submit the final payment. My thinking is that most commercial service/product providers require full payment upfront before delivering. Why should web design be any different?
This is just something I'm tossing around and would like to know what other designers (or service providers in general) think. Your input is most appreciated!