as JLee said, you are not liable for fraudulent charges.
It's good that you are concerned about risk of fraud. IMO a much more effective strategy would be to
1) place a credit freeze, preventing would-be thieves from opening accounts in your name
2) monitor your existing credit cards at least monthly
3) use a credit monitoring service to check for hard pulls and erroneous info on your reports (some services are 'free', such as Credit Karma)
Beyond that, keep at least one credit account that is >5 years old to avoid negatively impacting your credit score. If it is easier for you from a management standpoint, cancel newer cards or ones you don't really need. How MUCH credit you need varies substantially from person to person, but I haven't found much use for limits above what you would normally spend in a month + ~$10k. For any really big purchases, vendors are used to splitting them up into multiple payments over several months, because very few people can actually pay them in one lump sum. And if you are mustachian you will be paying off the balance each month regardless.
One advantage of canceling cards you rarely use is that your primary CCs will be more willing to raise your limit. One of the biggest things they look at is your total available credit.