Paying a loan or card with small weeky payments, rather than one larger monthly payment, severely decreases the life of the loan (and the total number of payments you'll make) since you're reducing the principle before it's had a full month to accumulate interest. This can be calculated w/ an amortization schedule
For example, let's say you have 4 years to pay off a $10k loan @ 9%. This will require you to make 48 monthly payments of $248.85. You'll pay a total of $1,944.83 in interest.
The alternative is to make weekly payments of $62.11. If you do this, all else being equal, you will make a total of 189 payments (19 weeks sooner than if you paid monthly) and only pay $1,782.83 in interest.
When the numbers get larger ($300k, 4.125%, 30 years, $1453.95 per month, therefore $223,421.31 in interest) the savings are larger ($300k, 4.125%, $363.49/wk, therefore 1340 payments and $187,728.59 in interest): you pay off the loan four years early and save almost 50k in interest.
Online calculator here: http://www.pine-grove.com/online-calcula...