Well, the old saying "the plumbers pipes are the last to get fixed", kind of holds true. I really don't wax my strings that often!
If their showing a little fuzzy or wear at certain areas, rub some wax on. I always tell folks to keep an eye on the lower part of the serving, if they are experiencing string slap or contact.
Now if you find a broken strand, change the string!
If you buy a new bow or different bow, make sure you have or order 2 strings for it!
Like having a spare tire for the ride!