The guys above me are correct, however if you want to ski a bunch of places, then I'd say you want to be closer to Summit County. Abasin is a very fun mountain, but not known for park. And, you will get bored of it for five days. There, you'll be within a half hour of Keystone, Breck, Abasin, Vail, Copper. You'll get a lot of different opinions on which mountain is better and why.
My opinion is: They all have good parks. Some better, some worse. Breck being a pretty popular choice. Vail is probably the most well-rounded mountain (i.e. they have verything from good park to great back bowls). However, it is the most expensive one. Also, if you buy a ticket to Breck or Keystone, then the ticket is good at Keystone, Breck or Abasin. Keystone has night skiing also. Not my thing, but others seem to like it.
This site will give some discounts.
http://www.skicoupons.com/couponsubcat.cfm/r/9/g/1/cc/28/cs/100
Whatever you do, do not buy tickets at the lift window. Local grocery stores (King Soopers, Safeway) and rental shops off the mountain have the best prices (about $15-$20 off ticket window) unless you know someone with a season pass or someone who works there. If it is spring break time, it'll be a lot harder to find discounts. You can always show up late to the mountain and look for people leaving. Bring a wire cutter and offer a couple of bucks for their lift ticket. Good luck
