Have you sat down lately and worked the numbers in your budget?
Gail Vax-Oxlade has an interactive budget worksheet which also shows by category how you are spending.
She suggests 35% for Housing, 15% for Transportation, 15% toward debt repayment and then retirement when it's paid off, 25% for the rest of life's expenses and 10% toward saving (or giving). Some are interchangable- if you get cars paid off, put an extra $100 toward your mortgage and get it paid off quicker saving you all the interest, then put the rest in an emergency fund to have 6-8 months of expenses covered in case something happened.
Try out her worksheet and figure out your monthly expenses and even see what you would use weekly if you gave the cash system a try.