With the whole deal with Games drawing power at 5V
How can you tell if the NES or the Cart getting damage overtime
You mean those aftermarket 3.3 V cartridges? The Famicom/NES operates at 5 V so those carts are dangerous to the console.
You probably can't tell right away, some people have fried a CPU or other components by using such carts for extensive periods of time. It's best to avoid using such carts at all.