Really Over Did This ...

Moving Day. Sat, Sep 9, 1967
Episode 2. Robbie Loves Katie. ...
Episode 3. Inspection of the Groom. ...
Countdown to Marriage. Sat, Sep 30, 1967
Wedding Bells. Sat, Oct 7, 1967
The Homecoming. Sat, Oct 14, 1967
My Wife, the Waitress. Sat, Oct 21, 1967
The Chameleon.

and there were more !

When lead actors like Fred MacMurray and Brian Keith are afforded special arrangements for their series, minimizing their shooting time to a degree, it's only natural that the supporting characters are featured more than they'd have been in a sitcom done more "normally."

Season 8 was all about Rob meeting Katie and marrying her. In my opinion, the storyline revitalized the series and likely contributed greatly to its ratings. Season 6 had focused on Ernie's adoption, Season 9 the triplets' birth, Season 10 the intro of Barbara, Season 11 the intro of Polly...

Speaking only for myself, one of the reasons I prefer M3S over Family Affair is due to the weddings. And those do require buildups and afterwards like the ones you've listed. Robbie & Katie's wedding day I find to be one of the funniest episodes of the series, a creatively written sitcom wedding with appropriately funny music and comedic acting.