Firewall notifications

I am getting pop up messages from Norton 360 that say that a computer (typically a printer or a cell phone on my home network) at a particular IP address is trying to access an application on my Mac. Most of the time I can tell that these are OK connections, but I am hesitant to say that a computer at a particular IP address can always access a particular app on my MAC. The challenge is that (unless I set everything on the network up with a static IP address) presumably the rule that I set up to allow a device to connect to an app on my computer today may not work when the connecting device has a new IP address tomorrow because of DHCP assignment of IP addresses: this potentially needs to a new pop up firewall request for the new IP address (which is annoying) and over time leads to creating rules giving permission to a lot of IP addresses to access an application on my computer (which potentially erodes security). Is there are way to avoid this?

PS - What would be the downside of giving the permission to MAC addresses instead of IP addresses?