No you don't. If you include "Hours" in there, what happens when you want to add that value to something else? "12 Hours" + "2 Hours" equals "12 Hours2 Hours" because you've made the field a string and that's how strings get added together.
Instead of Work_Time call your field Work_Hours and make it a number and know that every value in there is hours. When you need to display it you can always append "Hours" to that value.
