Q: My 2008 Nissan Sentra tail light/running light fuse keeps blowing. I'll change it and within 2 days it blows again. What u think?

The first thing you should do is replace the rear bulbs for the parking lights since they may be intermittently grounding out inside the bulbs. If still continues then replace front bulbs. If still continues then you will need to have wires and switch checked inch by inch for the short. The bulbs are the most common cause even if they work but they can short when hitting bump.