One of the complaints which I've heard leveled at Dungeons & Dragons third edition (and 3.5) is the "fifteen minute adventuring day" (among other names I've heard). I hadn't heard of that before third edition, though I suppose it could have been an issue in previous versions. Part of me suspects it came about after MMORPGs became popular. The third edition's emphasis on encounter balance and challenge rating probably exacerbated things, however.
In a nutshell, the problem is this: Many of the players' resources (like magic spells and special powers) are limited to a certain number of uses per day. So they get into a combat or two, blow all their resources, and retreat to rest up, replenish the resources, and fight the next battle or two tomorrow.
This was present in computer RPGs as well. Old-school gamers may recall 1st edition D&D magic-users as one-shot cannons in both pen & paper and computer RPG incarnations, or recall how forays into the Proving Grounds of the Mad Overlord or into the wine cellar allowed you to only get to the first door before running back to the nearest inn for rest. More recently, Neverwinter Nights addressed this issue by making it trivially easy to rest up at any time - which in practice meant, "after every combat."
Players and designers bring up this problem as something to be addressed by the upcoming 4th edition D&D game, and Paizo's own upgrade to the system, Pathfinder RPG. Except there are some crazies out there who maintain that this isn't a problem at all. And - with some caveats, I'm among the crazies.