I think you need to check your assumptions.
The 1st class Leisure Travel Card comes to 76,- or 68,- day depending which one you buy.
To get a 1-day saver pass for less than that you need to book weeks in advance. I currently see 66,- on Aug 25th and 26th, and then again on sep 1st....
Plus with the Leisure Travel Card you can spontaneously decide on the morning to go somewhere...