substituted service is a means of serving you without having to actually hand you the summons. Often times, publication in a local newspaper is a means of substituted service. Sometimes service is as simple as sending you a first class mailing to your last known legal address whether you get it or not. Your drivers license address is considered to be your legal address.

As well, if you do have a business and the business is in violation of the patent rights, your company can be sued. The address of your business is a matter of record. Depending on what type of business structure you have, there are often other officers or partners that can be served as a principal of the business.

Service will not fail unless the guy simply gives up or you close up shop and disappear.

How much time do I have?
for what? the plaintiff is only limited by the statute of limitations. I haven't checked but often times, a civil matter often is several years.

Don't make the mistake that if you hide until his patent expires that you are safe. He would be suing you for what is happening now.

What if I move to another state?
Patent matters are federal. He simply serves you at your new residence.