AC refrigerant will last a life time. It does not depend upon the usage. Unless there is a leak, no need to top up the refrigerant. If there is a leak, then the leak has to be identified and then topped up, else it is a waste.
Using the AC regularly will actually benefit the entire AC system and keep the coolant properly compressed. The service manual actually recommends using the AC at least for 5 minutes in a week to have the parts properly lubricated. You have to worry only if you are not using the AC for long.
Note : Using AC often in turn reduces your fuel economy. To be more friendly to the environment, you can use the AC only when if it is required and in appropriate speed setting. Running it in full blast always is not eco friendly
you see vintage acs still functioning today even with gases which are banned, that goes to show it never gets exhausted unless theres a leak.
along with the refrigerant the compressor oil to flows through the pipes with the gas while the ac is on. hence as sai said use the ac at least for 5 minutes once in a week. at least you will know that your ac is working rather than getting stuck in the rains with an ac that does not work. it would be a pain to defog the glass
which car do you have?