The Crimson Binome
Hero
My experience with slower healing in 2E and 3E is that players are just the right amount of cautious, as compared to 5E where they absolutely don't care about getting hit ever because they will definitely be fine by tomorrow.However, my experience with slower healing through 3e, and especially the slower healing from BECMI and AD&D 2e, is that it makes the PCs too cautious. Lower HPs = higher risk of death, higher risk of death = doing even more to avoid combat, doing even more to avoid combat often seems to result in the PCs taking a week or so to rest up before continuing the adventure (which can really be difficult when the adventure involves a ticking clock, or other repercussions from enemies).
Some of the best games I ever played in, back in 2E, involved managing resources against time constraints and pushing on while injured because there was no real alternative. There's nothing like it when the Thief takes point position to protect the wounded Fighter, because there's no time to rest.