Probably the most important reason why you want to be systematic about repeated notes is because you want to achieve clarity while you play.
The acoustics of the building might interfere with the clarity you seek so we have to do everything possible to make sure our playing is heard precisely as we want it to sound.
The basic rule is this: Shorten the repeated notes by half.
For example, instead playing two quarter notes which are repeated of the same pitch level, play two eighth-notes and two eighth-note rests.
The problem is when we have to shorten dotted notes which aren't easily divided by half.
Then we look at the unit value of the piece (the most commonly found smallest rhythmical value). With repeated dotted notes we simply shorten them by the unit value.
For example, if the unit value is an eighth-note, instead of the dotted quarter-note play a quarter-note and an eighth-note rest.
It's that easy.
But not quite because all the trouble begins in middle voices.
Make sure all voices with repeated notes are precise.
Then your playing will have the clarity you seek.
Actually, often it's the decisive factor between a good performance and a superb performance.