I am prescribed 40mg a day and have been for many years. I was told to take it only if i need it though. I get up every morning do my business and weigh naked. I write the weight on a calender everyday. I monitor how much fluid I have on me by the fluctuation in my weight. I have the doctors blessing to take more than 40mg a day if I need it. Many hot summer days I don't have to take it at all. I notice as my GFR falls I am experiencing a decline in output and I am having to take it daily now.
You must be careful with it. It does deplete your potassium. Going too low on your potassium is dangerous to pre-dialysis patients, just as going too high is for dialysis patients.
At some point the lasix will have less of an effect as your kidneys fail and you will need higher doses to get desired output and eventually that won't help so I am told.
I never heard of the kidneys drying up, unless thats a nice way of saying your "causing your kidneys to fail quicker". Which I suppose is a possibility. It forces your kidneys to work harder and that cannot be good for them.
DISCLAIMER: I ain't no doc