..or stress that each and every area and dungeon respawn independently. Just note when you entered a dungeon/area the first time if you want to be completely sure when it respawns - only really important if you leave something behind - that is any dead or living monsters, or you put anything aside in a chest - everything will be replaced when the repawn occurs. Most games you get to revisit and reclaim the areas that respawn after 6 months or maybe also 8 months. To my knowledge most will have completed before 2 years have passed. Take your time - no rush at all - only the final score reflects how much time you used and that's just a number - the real joy should be inside the game doing everything in your pace.
Also I don't think any of the fixed legendary items will become inaccesible even if you don't claim them before the respawn happens. Some random legendary items may be placed inside chests that can respawn - but again if you keep the respawn table in mind you shouldn't miss them, if you can access them in time.
I only once missed a legendary item, but that was in MM8 - I realized too late that a certain rock in Ironsand was more than a rock.
Should you ever lose an important item the Seer in Castle Ironfist will most likely be of service.