It depends on the dialect you're learning I think. However I think you can't make such generalization. I think in the middle of vocals like "arbeidet" they are usually pronounced (in the dialects I've came across). Also, the word "glade" I've listened it both with the "d" pronounced and also without it pronounced depending on the dialect. Usually you don't pronounce the "t" in the end of definite neutral nouns like "arbeidet", but I think that if it is a "t" at the end of an adjective, adverb or verb in the past tenses you pronounce it.