No real risk of spreading HPV through towels or any indirect contact.
It is really unusual to deal with genital warts for 20 years. Most people will clear the virus within a year, and over 90% will clear it within 2 years. Have the dermatologists recommended a biopsy? While dermatologists will usually get this diagnosed on visual inspection, a biopsy is often considered in atypical cases.
Most couples share HPV infections, but many people do not get, or notice, genital warts. In all cases, the same stats about clearance apply. If you have/had genital warts, your wife has probably been infected and subsequently cleared the infection. She would now be immune to this specific type of HPV. Couples transmit the infection once, but don't continue to pass it back and forth. That is why the doctors are not concerned about continued sexual activity.
I try to browse the expert forum before posting, but I forgot today.
I usually don't like to reply to questions that the doctors have addressed because any contradictions in my post would be wrong, but might add to confusion.
So......refer to the doctor's post.