SOL for lawsuits to collect a debt in CA is FOUR YEARS for both open-ended (credit cards) and WRITTEN contracts - the timeshare. They can make all the noises they want, the debt is legally unenforceable and if they DO try to sue you, you have an absolute defense in the expired SOL to have it thrown out.
Send the collection agency a cease and desist letter. You tell them never to contact you again about the debt as it is time-barred. Send it certified, RRR and keep copies of everything.
"Knowledge is Power - use it as you see fit !
I am not a lawyer or a member of the legal profession. My advice is based on research and experience, my own and others, some who practice law. You decide for yourself what actions you do or do not take from my advice.