Is my computer completely safe if AVG says the scan is complete and nothing was found, and how often should I run the scan?

Hello everyone,
I have AVG Internet Security on my computer, and I noticed that it says “Scan complete” but nothing was found. Does this mean my computer is now completely safe, even if I have used tools like Delta Executor or executors before? Also, how often should I run a full scan to keep things safe?
Thanks for your help!