This used to be a bigger deal when Saturday night stays netted you much lower fares than trips within the work week. The "old" back to back was buy a round trip ticke that included a saturday night stay to go to a destination and then buy a second roundtrip ticket to return home the same week and then go back to the destination after a weekend. Two "leisure round trip tickets" were often much less than the single "business trip ticket." The tickets with Saturday night stays were commonly $3-500 for domestic US travel, and tickets without Saturday night stay were commonly $1200-$2000.

Nowadays, it doesn't seem to make any difference whether you stay over a Saturday night. Many of my domestic travel fares are now $3-600 regardless of whether I stay over a Saturday evening.