I don't think I can "sell you" on a diff blind structure, but here is the one we use for my single table SNG's @ my place. I have used this structure for a 18 player tourney, and the game lasted approximately 3 hours. I'm not sure how well it'd work for a 30+ player game.
edit: The reason I slow down the increments in the later stages is because people like to play "poker" when teh table gets to be a little short handed, instead of playing the cards. Plus it makes heads up play a little more challenging, instead of an "all-in"-a-thon
edit: The reason I slow down the increments in the later stages is because people like to play "poker" when teh table gets to be a little short handed, instead of playing the cards. Plus it makes heads up play a little more challenging, instead of an "all-in"-a-thon