Full-time Flex schedule position?

I have an interview for a "Full-time Flex" position at Beth Israel in Newark. The criteria says I will be scheduled for three 12 hour shifts every two weeks and be expected to work two other days when I will be called in up to 2 hours before the start of the shift.

Has anyone worked a schedule like this?
What was it like?
Could I work more shifts than I am scheduled for?

Please share any experience with a flex schedule. Thanks.

Ashley
I was a flex employee when I first started at the hospital. As long as I met the minimum requirements for shifts (4 shifts a pay period, with at least half of those weekend shifts), I could put in for as many shifts as I was available for. I had no problem making full-time hours: I put in for 4 shifts a week and got all 4. Check with your staffing/HR department to see if you can put in for extra shifts...in my experience, most places will let you.I never had to be "on-call" like you describe, but nearly every day I'd get a call from staffing asking if I was willing to work that day/night or the next day. So it'd be up to me if I was willing to go in.