Are DT albums too long?
Hmm. I am a proponent that less sometimes is more; after all, the modern 79 minute album, in the 1970s, would have been two vinyl albums around 20 minutes a side. Double albums used to be a huge, massive statement by a band; now in terms of content they happen all the time. If you shave a minute and a half off of Pink Floyd's The Wall, arguably the most "double album" ever, it'd fit on one CD. Some of the greatest rock albums ever are under 40 minutes long. Less sometimes is more, you know?
As for Dream Theater and their albums being too long, the only one of theirs I actually think that about is BCSL; while I am sure the band didn't actively say, during the songwriting, "okay, we have seventy-nine minutes to fill, let's go about it!" it sure felt like they did. Given that DT is predisposed to writing longer songs, of course their albums are either going to be over 75 minutes long or only have five or six songs. BCSL's problem for me was it was six songs AND over 75 minutes long. A band sometimes needs to ask itself if it SHOULD fill up an entire CD.