I totally agree with you guys. And thank you for pointing out that you can't get storage fees if they never come back. That was a major "Duh!" for me.
Where I was before, we only required 30% as a deposit (not my rules), and sometimes that was a stretch. My favorite excuse not to give a deposit was "But you have my artwork.." Right, like if they took a car to be customer detailed, they'd weasel out of the deposit with "but you have my car..." In my mind, it makes sense to give something in advance for services rendered, no matter if you are turning over an item to be worked on or not.
I am currently working at 50% deposit on all orders and have had few, if any, problems with this. My only problem with this was one of my first customers dropped off several pieces to be framed, but claimed he did not have a business check with him, and he'd bring it in on Monday. Well, Monday came, and I needed to pad my order, so I ordered all the materials for the order. That afternoon, he still hadn;t shown up, and I called. I was told someone would be down soon. I finished the entire order, 13 pieces in all, and called the customer. It took 2 weeks(!) for someone to come in with any money, and when they did, it was for half the amount. I gave the guy half of the order (he wanted to take more, but NO WAY!), and he promised someone would be in the following week with the balance and to pick up the rest of the work. After 3 weeks and probably 5-6 calls by myself and Mike, this guy came in with the balance and picked up the rest of the work, but was rather rude about it. I learned my lesson with that. NEVER again!