Seat belt light stays on. Battery goes dead. Battery, starter, and alternator have been replaced.Fuses have been checked, trunk and glove box lights have been checked. Does the seat belt light pull enough juice to make batter go dead in a day and a half or should I look elsewhere for the drain.

You have a battery drain that should be diagnosed by:

Have a parts store test your alternator diodes; if OK then
Put an amp meter between battery ground and battery neg cable to read draw with key off, then remove one fuse at a time to find which one makes draw go away. Once you know which circuit is faulty, check all items on that circuit.

Some of the usual culprits are glove box door not shutting properly and making light stay on. Light in trunk staying on. Brake lights staying on because switch is misadjusted.

You have a current drain in your system. Using an ammeter identify the amount of drain. then pull fuses one by one until the drain disappears. Now you have the circuit that is responsible for draining your battery. You have to check all of the peripherals on that line.

Connect a amp meter in series at the + terminal on the battery and note the drain. there should only be a small drain caused by the clock ECT, Check for a light staying on in the trunk or glove box. Are you sure the battery is holding a charge?. connect a volt meter across the battery terminals and start the engine. voltage should be around 14 volts if alternator is ok.

Check to see that the trunk light and glove compartment light actually turn OFF when the trunk and glove box doors are closed. Also, if one of the diodes on the alternator has failed, it may still test "good." With the car sitting, ignition off, fully-charged battery, check to see if the back of the alternator is HOT. If it is HOT, replace the alternator.

Sounds like you might have what's called a parasitic draw on your battery. Parasitic draw is an electrical component staying on after you turn the car off (that isn't supposed to be staying on) and draining the battery over night. This can be caused by a multitude of things- the light in the glovebox staying on, an aftermarket accessory incorrectly installed to your vehicle, or malfunctioning, a factory component in the car malfunctioning and staying on, a power seat switch stuck on... the list goes on and on. The easiest things to check would be your dome lights, trunk lights, sun visor lights, glove box lights, and seat switches. Make sure the lights are all off after you take the key out and close the doors. Make sure none of the power seat switches are stuck on. If you can't find anything checking the lights and seats, you're going to need a digital multimeter connected to the battery to measure amps, to measure the actual parasitic draw. Once you establish how much parasitic draw there is (30 MilliAmps or less is acceptable), you're going to need to start pulling fuses one at a time to find out where the parasitic draw is coming from. When you pull a fuse and the parasitic draw on the meter goes away, you've isolated the circuit. Then you'll need to find what on that circuit is using power when it shouldn't be.
Good Luck :)

It's best to relate symptoms to narrow things down. I assume you are still getting a dead battery when trying to start even after replacing the alternator and battery.
Get a volt meter. Harbor freight sells them ridiculously cheap (about $5). Measure the voltage at the battery terminals when the engine is running. If it is at least 13.5 volts to 15 volts then the alternator is charging correctly. If it is 12 volts then the alternator is not charging the battery.

If the alternator checks out ok, then check for things that could be draining the battery when the car is off. Usual suspect is the trunk light. Put your cell phone on video record into the trunk facing the light, then shut the trunk. If the light stays on, its because the switch in the latch mechanism is faulty. WD40 might make it work, or just pull the bulb. Also, check the glove box light the same way. Good luck...Chris

Providing there is no trunk light, or glove box light or anything else that is staying on, the biggest culpret for draining batteries is the starter. Try replacing it with one from an auto wrecker, just in case it isn't the problem.
Make sure there are no power cables or wires burnt or cracked somewhere that are draining the battery.

Make sure there are no lights staying on. Check the interior light, the trunk light, glove box etc. When it is shut off, pull your fuses one at a time and see if any of them spark, that shouldn't be, when you put it back in. If that all checks out, it will likely be your starter draining it and it will need to be replaced.
Take a battery cable off, and when you put it back on, it should spark a little bit when the key is off. If it sparks a lot, i would guess it would be the starter.

YOU COULD HAVE WORN BATTERY CABLES OR ALTERNATOR BELT GLAZED SLIPPING OR NEED ADJUSTING.

what you do is uhook alternater wires and tape let car sit and see, if battery goes dead then thats not the problem. also have charging system and battery checked first. hope this helps.