My DD is just coming up to five months so I read this with interest, especially as I know THREE mums with babies the same age that are sleeping through 
We're normally up between 6-7 and then she has her first nap about an hour after she wakes up. I always hope for an hour, usually get 30-45mins.
Then we feed (EBF). Her next nap is two hours after she wakes up and by then I'm usually dressed and ready to leave the house so she sleeps in the buggy for an hour or so. She generally goes about two hours before she needs her next nap and by then I'm on the way home from wherever we've been!
The 3rd nap is a bit crazy. Last week it was from 4pm-8pm, yesterday it was for an hour. After about 7pm all hell breaks loose. She often won't sleep, cluster feeds, cries, is grumpy, wants to lie around kicking her legs about, has a laugh with her dad - there is no structure at all and every day is different.
I tried to feed her to sleep in a darkened room around 7-8pm for a few days and she hated it. Last night she fell asleep at 9.30 but wouldn't let me put her down until 10.30.
Then there's normally one wake up, between 3-4am but it can more than an hour to get her lie down again, either in the cot or in the bed. I'm lucky that the days and nights are pretty easy as otherwise I don't think I'd be able to cope with the evenings.
My policy now is just to do whatever she wants. I'm not really that bothered about having a routine as we've worked the days out gradually and I'm hoping the evenings will just happen naturally, like the OP says! She's got a bit of eczema and is teething too and I think these affect her more in the evening and night.
I had terrible insomnia as a child - i remember it starting when I was around 3. This is why I don't really interfere in DD's sleep. I won't wake her up if she's napping too long, for example, as it doesn't seem to affect her night sleep at all. One mum I know was shocked that I don't dream feed but whenever I've tried it she woke up at her usual times anyway so that was pointless!