The reason most people play is to have fun and socialize with others. Determining the percentage of playing songs and practicing drills over and over is an individual decision and will be different for everybody. When practicing students can do the following:

• Practice a new song from start to finish
• Do drills
• Play measures of songs over and over as drills ( 3 to 5 Minutes each)
• Play songs that they know for fun.

So there has to be a balance between drills to make progress in technique speed etc. and playing songs which is fun. Too many drills is not motivating and too many songs played over and over results in little progress on technique. In fact playing songs over and over that are being played incorrectly can actually reinforce bad habits and make the song virtually impossible to play with others in the future. Depending what the goal is would determine the percentage of Drills to playing. In the case of having fun and relaxing the percentage could be 10 to 15% drills and 85 to 90% playing songs. In the case of having to get ready to perform a song publicly the percentage could shift to 80% drills and repeating individual measures and 20% playing the song. As you are playing or practicing it is immense help to record yourself and watch and listen back. Most smart phones can shoot video. This will help you to determine what parts of the song to practice over and over. (Once again Drills). If you have a teacher their main job is to listen to your playing, identify parts of the song that need more work and suggest more drills. Most teachers can record the song you are learning at multiple speeds and even create play along tracks. Ask them to record each part at 3 different speeds including one that is hyper slow. Once you have practiced including drills you can judge the effect and then schedule your practice so that you are having fun and making progress.