Many business travelers pick Sunday evening or Monday morning flights to leave town, and return on Thursday evening or Friday. Flying on Saturday or mid-week gets you out of competition with the folks whose schedules align with a M-F work week. Sure there's plenty of business folks whose schedules don't align with that, but I think that's a help.

Holidays can be great for easy upgrades, but you have to be willing to travel on the actual holiday, not before it when everyone else does so that they are at their destination for the holiday.