This was the question posed by a Jefferson County milking parlor user group. The answer begins with "it all depnds". It depends on how good or bad conditions are now and what benefits can be attributed to the addition of rubber floors. To help answer this question, a spreadsheet was developed to do some cost and benefit analysis. This spreadsheet and an article "What the Research Shows about the Use of Rubber Floors for Cows" is available on the Center for Dairy Profitability web site at URL:
http://www.uwex.edu/ces/dairymod/cowcomfort/index.cfm#costs
You can also access the site by clicking through the CDP sequence of menus as:
Dairy Modernization, Cow Comfort, Costs
The spreadsheet has been used with a few groups of dairymen and they have advised on some of the cell entries. With certain assumptions, rubber floors can have a very rapid payback (less than a year) or they will never payback (paybak period > life expectancy). This suggests there is no one answer to the question and existing conditions and expected results influence the decision to use them or not.