The Collaborative International Dictionary of English v.0.48:

Overlong \O"ver*long"\, a. & adv.
   Too long. --Shak.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "overlong":
   dragging, drawn-out, extended, interminable, languishing, lasting,
   lengthened, lengthy, lingering, long, long-continuing, long-drawn,
   long-drawn-out, long-pending, long-winded, longsome, marathon,
   prolonged, protracted, spun-out, stretched-out