That does sound like an excessive wear rate. To improve the situation you may want to pay attention to how clean your rims are and maybe go for a different brake block compound. You could also adjust your riding style to what car drivers call 'hypermiling'.
Cleaning the wheels is important because dirt that builds up on the braking surface acts like an abrasive, wearing out your brakes and your rims. There are opinions on how best to clean the wheels, however, I ran out of posh bike-specific cleaning stuff a long time ago and moved onto raiding the washing powder soap. A tablet in a bowl of hot water with the brush from an old dustpan and brush is what works for me now. I then rinse off with cold water afterwards.
As for brake blocks, they do wear out and they do need replacing. I prefer to use the blocks with replaceable pads as I then do not lose my setup every time I swap out the pads - the toe-in and angle are what they were when I first set them up and I don't get any surprise squeaks. The replacement pads I use at the moment are dual compound, and, living in the UK I go for the Aztec branded ones. These may not be available where you are, just get the most common brand stocked.
If you over-rely on the back brake then that can wear down quickly. Try to use the front brake more than the back, obviously not always, but it does wear less.
Finally, make sure the brakes are not pointlessly rubbing whilst you are going along. They don't actually wear that much if they are, but check your brake setup, there are tips on that elsewhere on this site.