The passage of time is important to any campaign. Those who come from later editions and from video games may feel time to be a massive pressure, or so it seems to me from my observation of players. There are some things built into earlier D&D that take time, and no short period of it. Forget healing without a cleric, that's outside the standard experience (for the most part). These are simple every-day tasks that your PCs might undertake: training to next level, gaining new proficiencies, researching new spells... these things all take time. They aren't fly-by-night sorts of events.
Something has trained players to be very wary of the amount of time they spend preparing. Certainly, many adventures may be limited to a certain window of time: a bandit camp may very well be cleared out by someone else, grow much larger and more dangerous, or shrink as bandits drain off to go find some easier prey in a different region. This affect, change-over-time, shouldn't be taken as an excuse to run plunging from challenge to challenge. A battered party needs time to recuperate, prepare, and do the things that people do between adventures.
Not every adventure is immediate, in other words, and the mindset which leads one to think of every adventure as immediate is one that can lead to character death pretty easily. The ability to categorize which "quests" or adventures are pressing and which can wait is a potent mental power. Attacking a bandit's camp generally can wait, for example, while you prepare. Even if they're ravaging the countryside, it makes more sense to wait and prepare so you can be certain of clearing them out than it does to attack at once—why? Because the deaths that result from your delay will HAPPEN ANYWAY if you attack them and perish.
Preparation time is critical to success. A lot of adventuring is planning, and being caught without it can spell your doom—thus, slowing down and taking the time to tackle each adventure is a must.