Most airlines release seats 330 days in advance, but I'm not sure when HP does. Keep calling! Ask them if the seats are all taken, or if they're just not available yet - it's not clear from your post.
I'm thinking LAS will be a popular destination.
Also keep in mind some folks' (mine included) rule of thumb that if the ticket can be bought for less than about $400, you'll get a better value for your money by just buying it, rather than cashing miles.
One of the best uses of HP miles is on F tickets to Europe on BA. Another may be for transcon upgrades, but I wouldn't consider CMH-LAS a transcon.