It depends what are you mining.
Trick is if your cost of running mining is under what you can buy in that month then it’s good to buy and save electricity and at the same time get the same amount of coins that will be mined in a month.
Difficulty level changes everytime and benefit of buying in one shot gives you an edge as you dont have to wait full month to get all mined coins in your wallet.
Profitability also matters if you have large setup. So, I will advise compare your mined coins value with the current price then decide whether to continue mining or buy directly. As your rig life is also invested while its running and why to consume electricity if it can be saved.
