On general note: Always work with retainer/deposit payments. Do 30/70; 40/60; 30/30/40 for longer project or any splits you feel comfortable being able to press onto client. Alternatively, signed off parts, or work finished by month,...
It's absolute staple of almost any other kind of business, it needs to be standard in our industry too. In my experience, I have never met a single client who would have any issue with it (but one client tried to give funny counter-conditions...but that is different talk).
It's same important, if not more, than contract itself ( which quite often, is much more a psychological thing. Good rules makes good friends ).
This way, you'll never worry about loosing the total sum of project and it's much better for studio's cashflow too.