Mom is 41 miles and an hour and a quarter from us through heavy traffic. Each trip costs us $20 and she seems to have a daily crisis. Mom is out of touch with how expensive things like gasoline are now, plus she is comfortable in her current facility. For our own convenience, we want to move her closer to both friends and family but we are not sure how she will feel about it. Also, we are both in our 70's and tire easily.
I'd follow the advice others have already mentioned - don't respond to "emergencies" other than by phone. There's really nothing the staff can't handle. Limit your visits to whatever you can handle. Once a week sounds right. I don't know that explaining your reasons for reducing your visits will get you anywhere. I'd just keep it simple. "See you next Saturday, Mom."
However, in the future, if your mom's condition worsens to the point where she's really not engaged at all at the community, I'd see no reason to leave her so far away.
If mom is comfortable in her current facility and her MD feels she is safe there, let her be. She has friends, too, and won't want to give them up. Just make it clear you will visit once a week and any crisis that pops up in between will have to be handled another way. Network with the onsite management and custodians, friends and neighbors to at least check on her and report back as to how serious her crisis is. Notify her police department/911 about her medical conditions and how to contact you if they need to.