We put the salt out of our water softener on ours last year when we had the big freeze thankfully it did'nt have any effect on the tarmac but we only done it two or three times and only where we really needed it.
Also remember, that in most cases you only need to tarmac the 2 strips of it that your tyres will move over, you can then also use these strips to walk on. means you are minimally effecting the tarmac.