It's been decades since I've seen a 4-hour charger that didn't include a mechanism to shut off the current at around full charge, but the mechanism may be crude, like a thermostat. The last time I did, it was for a TI calculator with fast-charge nicads designed with a shortage of chemical on one set of plates to make overcharging impossible (in theory).
In practice, best battery life is probably achieved with fast chargers that aren't too fast and that don't overcharge since they contain good shut-off mechanisms that rely on temperature difference, rate of temperature rise, rate of voltage change, etc. Also cells last longer per charge when charged fast since that causes larger crystals to grow during the charging process.