The lifespan of brake pads is not only dependant upon environmental conditions but also very much upon what is put into them.
I'm compelled to point out there is a massive difference between the compounds that manufacturers put into brake pads. I've no idea what compounds are actually in them but I'd describe some as "rubbery", some as "gritty", and many in between.
I've had brake pads that, no matter what I do, will shudder or squeal - I dare say they have too much rubber in them. Similarly I've had brake pads that grind away my rims faster than they wear away themselves. Some work well in the dry and bad in the wet, some the opposite.
Whilst "normal" will vary according to your environmental conditions, don't forget to consider your own brake application (sounds like you don't use the front brake enough) technique, and - my primary point - that brake pad compounds do vary wildly.