Now if you really want to emulate the Prophet (pbuh)...

Prior to the start of Ramadhan, my ustaz had asked me how many how many years I have fasted, and I said that this would be (is now) my sixth Ramadhan. He replied that I have almost caught up with the Prophet Muhammad (pbuh), who fasted for eight years. (The command for Muslims to fast during Ramadhan is located in verses 2:183-5. According to Maududi, "The greater part of Al-Baqarah was revealed during the first two years of the Holy Prophet's life at Al-Madinah.")

However, if we really wish to emulate the Prophet (pbuh) in his fasting, we need to fast a lot more than just eight Ramadhans. From Saiyid Sulaiman Nadwi's book, "Muhammad, The Ideal Prophet: A Historic, Practical, Perfect Model for Humanity" (translated by Mohiuddin Ahmad), page 101:

"The Prophet commended keeping of fasts throughout the month of Ramadhan. But, in addition to these, he punctuated every week with a fast or two. 'When he took to the keeping of fasts,' says 'Ayesha, 'it appeared as if he would never give them up.' The Prophet forbade his followers to prolong the voluntary fasts beyond a day at a time, but he himself used to fast continuously for days together without even taking anything during the night. If his companions tried to emulate him, he dissuaded them saying: 'Who amongst you is like me? My Lord provideth sustenance to me.' Normally, he kept fast for the whole of two months during Sh'aban and Ramadhan, the 13th, 14th and 15th of each month, the first ten days of Muharram, six days following the 'Id-ul-fitr, and on Mondays and Thursdays in every week. In this manner did the Prophet teach his followers how to keep fasts."