I started in 1980 so most of my experience with classic D&D was with AD&D. In large, higher level (i.e. above 5th) parties with few clerics, it routinely took multiple "rest days" for the cleric(s) to memorize and cast enough healing spells to restore the party's hit points. This was
routine. I guess you could do a reality check by looking at the pool of hit points for a large party and comparing that to 1e
cure spells and slots. I'd also note that
@Lanefan liked my post pointing this out--it's just that he sees it as a feature, not a bug.
ETA: Here's a start. A 7th-level cleric in 1e can cast 4
cure light wounds and 1
cure serious wounds. As I recall, it takes 15 minutes per spell level to memorize spells (in addition to sleepytime). So assuming the party is tapped when they rest, they first have to sleep. Then the cleric prays for a couple hours (if only memorizing the
cure spells), at which point they can do 6d8+1 healing for the day, or 28 hit points on average. Then you can repeat this process, and again, and again, until the party is healed up. Then, you'll want to rest again so the cleric can memorize
all their spells, not just the
cure spells. Then you're ready to play the game again. (Any unfortunate random encounters during this time will, of course, delay the process, as rest is interrupted, more damage is incurred, and spells are consumed.)
It's possible 2e resolved this problem/feature (depending on your perspective)--I don't really know. I also know it wasn't an issue with 3.x, because PCs were always festooned with
cure wands.
And...I really don't care.
I don't like devoting days of game-time and significant play-time to rest and healing mechanics. If this has never been a problem for you, or if you
do like the effect of these mechanics on your game (e.g.
@Lanefan), then you shouldn't care either. I'm not trying to convince you of anything--merely explaining why "fast healing" in games such as 5e or
Shadowdark work just fine for me. As always, you do you!