Used one already today. They work well for paying bills. I wonder if your business customers make one big visa card purchase or a bunch of small purchases as they need. I've been mostly buying exact amounts for what I need if they don't have a giftcard or direct bitcoin option.
Discussion
There's no right or wrong way to do it, which is why we see both methods fairly equally (ie, one card for spending over the month or numerous cards for specific spending)!