Watch the Duration of Chords online guitar lesson by TrueFire from Play Acoustic Guitar 4: Rhythm Approaches
Duration of Chords - Technique #3 is a video guitar lesson presented by Vicki Genfan and is sourced from Acoustic Rhythm Survival Guide.
Now this technique may be more useful at first glance for the songwriter... however, I think you should also consider experimenting with it in the context of a cover tune you may want to rearrange. By simply playing each chord for a longer or shorter period of time we change the whole 'cadence' or 'feel' of the song or section.
Try it with either a song of your own, or a favorite cover tune – keep the progression the same, melody the same – but now you'll find that you'll be stretching the melody out longer, when you're holding the chords out for longer time periods, or packing it in more quickly... both will have a dramatic effect on the song.
When using this tool in songwriting mode, you might try holding the chords for a longer duration when you've got more lyrics that you want to sing, and then moving to a quicker chord change pattern when you have fewer lyrics – and can hold them out longer. But ultimately – you'll decide what sounds and feels right to you. I personally find it a really great tool for songwriting and it's so simple that sometimes I forget to use it!