I came to hate changing my DIY CO2 bottle every week, so I stretched it to every 2 weeks, which sometimes was every 4 weeks when I would forget it. But, really, it isn't a very big or hard job. And, it isn't expensive each time you do it.
If you have high light intensity on your tank, then stopping the CO2 will very likely result in algae problems a couple of weeks later. But, if you have low light, stopping the CO2 will make the plants stop growing for awhile, but probably won't cause a major algae problem. Plants have to adapt to living with or without CO2, so stopping the CO2 would make them adjust their internal production of various enzymes, and that is what would stop their growth for awhile.