Being new at Royal Mail absolutely sucks.
If you can get through the first 3-4 months though, it does get better as others have mentioned, you get quicker, you become a hardier person less bothered by the weather, you learn all the little tricks to make life a bit easier.
Still I agree with most of what you said, we get treated like idiots and lied to, almost daily, by our 'managers'. I also remember on my first walk, the guy on the walk next to me who did the other much easier part of the same area, he used to wave to me at like 1pm as he was just about to finish. I'd be out til 2.30-3.15pm each day. How is that fair? I was fairly new, which could explain maybe 30 minutes, but when there is an hour and a half to 2 hour discrepancy, you know he's onto an good thing.
I agree there is too much discrepancy between between the easy walks and the hard walks. P&L has evened things out a lot more nowadays, but until they properly time people on their walks over say a few week period, then things will never be fair. You just get used to it mate, the Royal Mail isn't fair, once you've realised that, then you have a decision to make. I was reaching the end of my tether with my own walk and would have left if it carried on, thankfully P&L came in and I got put on a totally different walk that is probably 50% easier than the trudge I had previously.