If your tile floor is properly maintained, you can expect it to last 20 years or more. You will greatly enhance the life of your tile floors or walls by using a properly installed cement backer board.

Properly maintained tile walls installed over a cement backer board can also last 20 or more years.

It is better to remove the existing vinyl, but if it does not cause a transition problem from one floor to the next and/or if it does not cause a problem with the installation or removal of appliances and doors then it can be done. Keep in mind though that you may want to remove and raise your base boards so they have the proper reveal.

No. Many people with large dogs have hardwood flooring. Your dogs will scratch the floors and it will cause more wear; however, unlike vinyl and laminate floors, hardwood can be refinished in the future. Keep in mind that even under normal circumstances, your hardwood floors will scratch. That being said, as hardwood floors age they tend to mellow.