This is what I plan to implement in my game. It is more generous than the 5.5 rules but I want characters to be able to use their stealth if they have invested in it.
HIDING RULES
When you are hidden you cannot be detected by sight or hearing, although creatures with other senses might be able to detect you. You cannot be targeted directly by spells or other effects but the space that occupy can be targeted via area of effect spells or sheer luck.
You can attempt to become hidden by making a Stealth check as long as you are obscured or have cover. The Stealth check is made with disadvantage if you are only lightly obscured or have less than 3/4 cover. The check is compared to another creature's Perception check or Passive Perception score depending on if the creature is actively searching for you. You remain hidden until immediately after you meet one of the conditions that negate the hidden condition or require another Stealth check.
Conditions that automatically negate the Hidden condition:
1. Attacking
2. Casting a spell with a Verbal component.
3. Making any noise louder than a whisper
4. Ending your turn in an area with no cover nor obscurement
5. The DM decides you no longer meet the conditions to remain hidden.
Conditions that require another Stealth check:
1. Moving more than half your speed
2. Moving through an area with no obscurement or cover.
3. Ending your turn in an area that is lightly obscured or where you have less than 3/4 cover (made with disadvantage as per above).