It appears to me that MBNA has a practice to increase one's credit limit every three months. Almost exactly three months ago, I reported that MBNA bumped up my credit limit by $500 to $7,000. Yesterday I noticed that the limit is now $7,500, another $500 jump after three months.
So here is my credit card inventory (order by preference):
ShareBuilder Visa Platinum: $2,500 ($25 credit for every $2,500 purchase)
MBNA MasterCard: $7,500 (1% rebate, 20,000 points accumulated)
1st Tech Visa Platinum: $5,000
NetBank First USA: $2,500
Providian Visa: $4,500
Total Credit Line = $22,000
(I'm paying off all credit card balances month except for 0% APR promotional periods so interest rate is not important for me.)