30 (28-29 really) minutes is too long for a sitcom. Channel 4 and ITV ended up at about 23 minutes because of ads and it turned out that a 23 minute episode really is the perfect length. I find 30 minutes can drag on and you really have to want to watch to do that.
Let's have a debate/fight about it.
The exceptions being IAP 1&2 which are 28/29 mins each I think?
Channel 4 or ITV would often make 8x23 minutes, which is just over the 3 hours of 6x30 minutes. 8 episodes of Alan or 6 longer ones? Tough one.
So, that's why I find ITV sitcoms overall slightly more digestible than BBC ones (which is not to disparage the latters). Although, wasn't it David Croft who once said that sitcoms needed to be 30 minutes long at least?
So, is 30 minutes on the dot more suited for sketch shows that sitcoms. I'd say yes, too.