I also take too many photos and delete a lot, so I'm going to try to lessen how many photos I take. I'll also backup or format every month or so.
I'm not saying you should take less photos. It would be against one of the main advantages of digital photos.
One possibility is to delete the unwanted ones not "every day", but when your card is, say, 50% or 75% full.
The "principle" is that those unwanted photos (files in the card) are using specific spaces (compartments) of memory (of the card). When you delete them, those same spaces get to be available for new use. In some "extreme" situations, the same memory space is used again and again, while other spaces are used very infrequently. The "overused" memory spaces get to a point that they start failing (not saving the photo / file correctly), even if the other (less used) spaces are free and working correctly.
So, in some cases, very few memory spaces in the SD card might be failing, and then the SD card turns to be almost useless, even if most of the memory is potentially working correctly.
The technical details and the specific situations where this happens are a little more complicated than that (and the "lingo" I used is also not so technically correct either), but my intention is just to explain the main idea / goal.
For a specific memory area to start failing, it would need 1'000s or even 10'000 times of use (between writing and reading the same memory space again and again and again...).
So if you keep those unwanted photos / files a little bit longer instead of deleting them "immediately", the next photo you shot will certainly occupy a different memory space (instead of using the same space you just cleared by deleting the previous photo). Again, this is not exactly technically correct, but it is just to give you an idea of what I mean.
The bottom line is:
enjoy your camera and use it (and the SD card) as much as you want and need. Having multiple safe backups is what is going to really save you from a potential disaster. The rest is just hardware
.