You don't use the weaponlight 'til you're sure you need it. I have the Streamlight M6 weaponlight/laser sight. It has a easily reachable two-way rocker switch (momentary/constant on) and a selector knob to choose the laser only, light only, both or off. I keep it set to laser only to allow rapid use of the laser but prevent accidentally revealing my position with the light. If the light is needed it's a simple twist of the knob. It's like 90 lumens in a tight stream, which is enough to temporarily dazzle/blind an attacker, and by the time he sees the light, he'll be about a 1/2lb of pressure away from being a dead man. The light is for target ID only. The laser is not that obvious unless you have a very dusty house, and it definately makes the gun point-and-click without having to try to acquire the sights in the dark.

As far as returning to zero, I haven't seen a problem. I'm sure at 20+ yards it might be off enough to cause a poor hit or miss, but considering that the average range for an OUTDOOR defensive pistol encounter is 21 feet. 7 yards. The distance likely against an attacker in your home is much less than that. How big is your bedroom? 10'x11'? 12'x12'? How long is your hallway? 15 or 20 feet? The error at these ranges might be a couple inches, which is inconsequential. It's definately less than minute-of-perp.

Mike