Math aside - I commend you for the extra principal reduction made. Now only 347 payments left!Well as of March 5th so for far I've reduced the principal by around $1650. I made much of that yesterday.
Y'all made me run numbers lol. A couple of comments: I'm only 9 months into a 30 year mortgage. The total prepayment has knocked off only 4 months off the original loan but it will have saved me $4457 in interest over the life of the loan. If I stuck $1650 in an investment returning 6% per year, compounded and assuming none of that 6% is taxed (I assumed stock growth and no dividends) then it appears I would be in the same position in year 27 assuming I sold the investment that year and was taxed at a combined federal and state rate of 26%