Trial codes are still active?

I used a demo/trial code aproximately a month and a half ago for Factions, Nightfall, and Prophecies. A few days later I went ahead and purchased the Game of the Year Edition of Guild Wars. I immediately began playing the regular storyline and never thought twice about Nightfall or Factions as I assumed they would be expiring shortly. However, yesterday I noticed that I was able to take quests that one of my friends couldn't access, so when I researched those quests I discovered that they were Faction quests (which should have expired several weeks ago). When I checked on my active keycodes, it states that yes I have purchased the game of the year edition. It also lists my 3 trial codes, but it only lists the code for Prophecies as being expired. Nightfall and Factions are still active... yet I activated them well over 14 days ago.

Is there a reason they are still active and I can still do the other campaigns? I have every intention of purchasing them both once I've completed the original, but with the trial not deactivating, will it cause any problems?

I don't see why not. Whether you are using a trial key, or a full-access key, everything you do is still registering to your account/.dat file.