Well, my LS just rolled over to 143,000mi's and I am afraid to drive it on long trips now. Exactly how many miles should i be able to get out of it? Just wanting to try to feel more comfortable with it. If it does die,,,,(god forbid) I can just get a used 3.9L and drop in it.

How does the engine sound? Any loud knocks or ticks? Are the accessories making any groans or whines? How does the serpentine belt look? Has the tensioner been replaced since you turned over 100k? What are your maintenance habits like? When were all of the fluids changed last? Trans fluid, diff fluid, engine coolant? If you've kept up with regular preventive maintenance items, you should be just fine. But if it's been neglected in the past it may be time to trade it in for something newer, or at least with lower miles.
Its hard to tell sometimes when something is getting ready to break down unless you've dealt with problems in the past that may now be exhibiting symptoms of wear or potential failure again. If you're unsure of anything, or there is anything that has caught your attention recently, or even if there isn't, it might be wise to take it to a shop and have it inspected for potential problems.

Well, I havent had it all that long, i have put about 10,000mi. on it, But bought the car at a great deal. There is nothing wrong with the car, no ticks or knocking, everything works ideal. There are the 2 things that i need checked like the famous knocking in the front when you run over small bumps slow. and for some reason when im goin and kick on it it will run up to about 4500rpm and start jerking, but if i let off or the gas just the smallest about it will stop.

Sounds like a screwy coil. Those seem to go bad no matter what. Not much you can do with that except wait for it to throw a code and set the CEL. Unless you want to spend about $400 to replace all of them. (that's only if you do the work yourself)

Well, I have 142,700 (01 V6 sport auto) and mine runs better than ever (knock on the wood). I think you should change all the coils and all spark plugs. It's better to change em all together than going back and changing every single one after every two months. Well in your case maybe it's a bit more work (injectors or so), but still you can't go wrong with new coils. I think it's easier to change em on the V8 and just change the fluids.

I don't think that you should have any problems with it. It seams to me that these cars get better with higher mileage.

Go for 500,000 miles!

I've "heard" that the 1st gens can go over 200,000 easily as long as you maintain it well.

There was a guy here recently that turned 160K without any major problems. I think that once you fix all the common problems these cars are durable.

I saw an LS on ebay one time before that had 200000+ miles on it, but the check engine and airbag lights were on.