As for me, speaking generally and without regard to any particular parish, jurisdiction, etc., I enjoy long sermons if they are well-organized and well-thought out, i.e., something in the nature of a mini academic discourse which presents a certain thesis as the interpretation/application of what was read, which then explains how this can be seen in the writings of Scripture and the Fathers and also how it can be applied now, and which demonstrates careful study of the topic. The sermons of the early Fathers certainly all seem to be of this type. The most painful are long sermons which do not appear well-thought out and which, rather than presenting such a synthesis on a particular topic for edification, are merely a series of unconnected thoughts or, even worse, "feelings" on a particular issue. These strike me as the presentation of unpolished drafts.
In my history of pre-Orthodox church attendance, I often felt perturbed by some of the Protestant sermons which started off with a reading of the Biblical text and then went off into the pastor's own thoughts for the day, without actually explaining what had just been read or trying to ground it in any sort of doctrine or tradition.