I use both monitors and headphones for my production/mixing/mastering. I have just recently purchased my monitors(krk rokit 5's) and am very pleased to have the option to now use monitors, but I still continue to use my headphones(Dre Beats Studio...don't judge me they were a gift but I'm actually pretty pleased with them too). When my track sounds good in both the headphones and threw the monitors i consider it done. I just thought I'd contribute to this thread by explaining my current production/mixing method.
*NOTE* I consider myself somewhat of a beginner producer.