It's definitely gotten easier for us. As for giving him a cup in the daytime, it might make the transition easier for him. I tried giving Megan milk from a sippy when I was still home, but honestly, I found it easier and she drank more when I nursed her, so I mostly gave up! If you're only working part time, he could still get the milk from you when you're home. Because he's younger, you really want to make sure he's getting enough, it's true, but it's probably only 2 - and eventually 1 - nursing that he's missing. Most bf babies take between 4-8 oz per feed, I imagine, so one missed feed won't be so much - and maybe you could make it up when he gets home...sort of cluster feed the milk before bed...I'm not sure.
Closer to a year, as long as he's getting dairy from other sources, it's not such a big deal too- especially if he'll take water.