Is it true that once a dog has urinated many times on a carpet that one must
replace the carpet because the urine scents cannot be removed by cleaning
the carpet?

My folks have 2 dogs that have urinated all over their carpeting for the
last 10 years. It's getting worse as my folks get older. They are in their
80s and don't seem to have the interest (or energy) to house train their
latest 2 dogs.

Also, is it possible to house train 2 dogs who have been urinating on the
carpets and rugs for 5 to 10 years (the dogs differ in their age)?

Thanks for any info or help

Chip