I do the same thing. Couple of things you need to know;
DLC is region locked, so if your game was purchased on US account, DLC needs to be too.
You can play the MP part of a game, purchased on your US account, on your home account as long as 1 of those 2 accounts has PS+. So no need to stay logged in US account after the purchase was made. Same is correct for DLC
It's not illegal to be buying games this way, i've contacted Sony US multiple times now, they just don't recommend it and let you know you can't complain if something doesn't work as you're planning.
Aside from all that i love this ability and have been doing it much more since the PS4 has arrived as games are much more expensive if i buy them here. It has also made me go digital somewhat lol. GTA5 for example is 70 euros here and 60 dollars in US. 60 dollars means 46 euros deducted from my Credit card which is almost cheap!







