Electrum is a deterministic wallet which means that all address specific private keys are derived from one single master private key which in turn is derived from a seed. That means all the addresses in your wallet past, present, future, receiving or change can be recovered with a one time backup of your wallet file and/or seed.
Unless, as in the OPs case... there is no seed and his wallet is NOT an HD wallet...
seriously, people need to start actually reading threads all the way through before jumping in at the end with advice that is wrong...
Exactly. My Electrum wallet was imported from the private key so there was no seed. If I disable change addresses, will a single backup of the wallet file be all I ever need?
OP, if you don't create or import any other keys in your wallet... then you should be fine with a single backup of the wallet file, as that will have whatever private keys you currently have in your wallet. Should you, at a later date, import (or create) another key into your wallet, you would need to make another backup.