4 part series

What's everyones thoughts on the trend from the show over the past few years of doing 4 part series ? I sometimes feel that what ends up as 4 could have been 3 episodes. For instance the current series, the first and second episode feels like they could have been edited to work as one episode. I'm not meaning to come after the boys because I'm happy with whatever but it does feel like we are more likely to get a 4 parter these days rather then something like a great one off.