the $100 limit just keeps us (me) in check. sometimes i'll put gas on that card too (~$60), but i was deep in credit card debt for years and it scares me a bit to just put $20 here, $15 there, $40 there... we like to keep it to things that we have budget lines for... groceries, gas, car repairs, tires, et cetera. we're not worried about getting cash back or working the points system or anything like that, we just want to build up some travel points so we can fly somewhere once a year.

i also have an REI visa that i used to use for work purchases. my employer reimbursed all my gas purcahses and any home depot or paint store purchases i made, so i would rack up my REI dividend on the company's dime. i got a ~$190 dividend last year just from work expense reimbursements. i put that one away in exchange for the southwest card, though and don't have that job anymore :\