Your flying won't come close to the levels necessary for a corporate discount. Simply buy the least expensive r/t fares; unfortunately, these former Shuttle markets now have the $100 change fee on all discount fares so other than same day standby, the level of flexibility is limited.

I've been doing LAS/LAX or LAS/RNO weekly for 7 years and have made 1K on segments each year during this period. With the no change fee on the old Shuttle fares, I never seriously considered switching to Southwest, although I do fly them periodically (LAS-RNO).

If I were starting the process from scratch today and weren't already a 1K, I'd probably do it with Southwest given their lack of change fees and the ability to reuse unused tickets on their website. The only downside is they require upgrading discount fares to full Y fare for standby.