air locks bad for secondary?

So I have 3 gallons of mead in single gallon containers aging (currently 6-7 months old) with air locks. I was recently told I should not have used air locks for secondary and aging as it could cause oxidation.
Should I be worried and replace them with rubber locks or leave as is?

Temperature swings cause pressure changes.

Mead gets warmer, air pushes out the airlock.

Mead gets colder, new air comes back into the carboy through the airlock.

The mead should be fine but yes, best practice (if fermentation is DEFINITELY finished) would be to plug it.

I, however, usually leave an airlock. Don't have any problems with oxidation thus far.

Cheers.

Once the secondary are filled all the way up to the neck you're in good shape. Wine, mead, beer all the same.

An airlock allows release of pressure if any is produced.

A bung will not allow this. Carboys are not designed to withstand pressure. Using an airlock is therefore advisable.

Mdindy, the above responses are all correct. To put it more bluntly, what you were told about airlocks in secondary is just plain wrong. As in, the complete opposite of correct. In secondary, your wine/mead is still fermenting and needs to be able to expel carbon dioxide. Even during aging, CO2 is still coming out of solution and needs to be able to escape.

A solid bung traps these gasses. Let the wine breath. I would only consider a solid bung after about a year of aging and once you are sure wine is fully degassed. Even then, a standard airlock is still fine.