Campbell
Relaxed Intensity
I'd argue if there has been a meaningful shift it's not necessarily one of delayed versus instant gratification. My most recent experiences with AD&D (which were less than a year ago in an admittedly dungeon crawl oriented game) taught me that leveling past 6th level or so was not really all that exciting. New magic items were far more interesting and had a larger impact on character power (I include spell scrolls here). I had to almost force myself to continue to care about leveling up - my dwarven fighter had some pretty good saves, more than enough hp, hit things pretty well, etc. I almost had to force myself to keep tracking my xp. I think the trend over time has been to de-emphasize gear and focus more on character potency. It's more reliable sure, but depending on treasure table RNG is not really less immediate in my experience.