1E: Lasted until dispelled or the person did an offensive action.
2E: Lasted 24 hours or was dispelled or the person did an offensive action.
3E: Lasted 10 minutes/level or was dispelled or the person did an offensive action.
3.5: Lasted 1 minute/level or was dispelled or the person did an offensive action.
4E: Lasted until end of next turn or the person did an offensive action, strong concentration by caster (target had to stay within 5 squares, sustain standard to maintain)
5E: Lasted 1 hour or was dispelled or the person did an offensive action or the person casts a spell, concentration by caster
5E is not quite as good as 3E (the casting and concentration limitations weaken it), but is a lot better than 3.5 or 4E (although an invisible wizard could still cast some non-standard spells for 4E).
It can actually be used to send a sneaky PC into an area to investigate again.
2E: Lasted 24 hours or was dispelled or the person did an offensive action.
3E: Lasted 10 minutes/level or was dispelled or the person did an offensive action.
3.5: Lasted 1 minute/level or was dispelled or the person did an offensive action.
4E: Lasted until end of next turn or the person did an offensive action, strong concentration by caster (target had to stay within 5 squares, sustain standard to maintain)
5E: Lasted 1 hour or was dispelled or the person did an offensive action or the person casts a spell, concentration by caster
5E is not quite as good as 3E (the casting and concentration limitations weaken it), but is a lot better than 3.5 or 4E (although an invisible wizard could still cast some non-standard spells for 4E).
It can actually be used to send a sneaky PC into an area to investigate again.