Player Prefs and String Concatenation

Hi,

I'm trying to save the best level times for a mobile game I'm making. There's a level select screen and underneath each level button is the best time that level has been completed in. At the moment this is all taken care of with arrays, etc.

But getting PlayerPrefs to save these times is where I'm having trouble. At the moment I have this part of a function that runs every time a level is completed:

 if (levelTimes[levelNumber] < time){ // set best time
 
                 levelTimes[levelNumber] = time;
 
                 PlayerPrefs.SetFloat("Level Time: " + levelTimes[levelNumber].ToString(), time);
 
             }

And then when the game starts up, I try to get that time by calling this:

 noOfLevelsCompleted = PlayerPrefs.GetInt ("LevelsCompleted");
 
         for (int i = 0; i <= noOfLevelsCompleted; i++){
             levelsCompleted[i] = true;
 
             levelsAvailable[i] = true;
             
             if (i !=9){
                 levelsAvailable[i + 1] = true;
             }
 
             levelTimes[i] = PlayerPrefs.GetFloat("Level Time: " + levelTimes[i].ToString());
         }

Any idea why this isn't working? Will I have to create a separate PlayerPrefs for each level and save the best time like that? I could probably figure that out, but it seems like a bit of a roundabout way of doing it to me.