Consuming these substances won't wear out your kidneys. As long as your kidneys are functioning fine, you should have no problems. The problems arise when your kidneys are not already functioning well and you introduce substances that the kidneys have to clear from the body. For instance, if your kidneys were already impaired, you would retain magnesium and sodium.
With respect to C-Vitamins, it's best to use ascorbate salts such as magnesium ascorbate, calcium ascorbate, etc. Plain ascorbic acid will leach minerals from your body and then lead to low mineral levels.
The standard for determining the functional ability of your kidneys is to have a blood creatinine test, and then calculate the GFR (glomerular filtration rate) from there. A GFR of at least 90 is optimal; if it's less than 60 you should be careful about introducing excess magnesium and sodium, and consulting a doctor is best in that case. Between 60 and 90 you're still probably OK at the levels you are taking. GFR levels are fairly stable within a range of
+ 10 points, so a creatinine you had a year ago would still be OK to look at.
Here's an online GFR calculator:
http://www.qxmd.com/calculate-online/nephrology/mdrd-egfr