How long will a Northstar last?

I've seen a few late nineties Devilles for sale with over a half million kilometers (300,000 miles). These are selling for a few thousand dollars and look appealing provided they last for a few hundred thousand kilometers. I'm assuming these were driven primarily on the highway. I guess the mindset is that highway driven cars are in better shape despite their mileage.
Are the repair costs much higher than say, a Buick or Olds. I currently drive a 1988 Buick Park Ave with 400,000 km (275,000km on the second engine) and it has been quite reliable but after 18 years of Canadian winters, the body is starting to show its age.

The Northstars do last a long time if they are taken care of. The major reason they fail is lack of cooling system maintenance. I have seen a few with 300k-400k miles on them.
And yes, a Cadillac is going to be more costly to own than a Buick. There's a lot more technology in a Cadillac than a Buick. But a Cadillac is usually cheaper to own than a Euro luxury car.

Thanks Caddydaddy,
Cooling system maintenance you say. Do they have Dexcool in them from the factory? Could that be the problem?

The 1995? and up GM cars have the Dexcool, but the earlier ones can suffer from the same problems. They seem to be pretty sensitive to the coolant going past it's service life, turning acidic and eating at the headgaskets. It's just important to make sure that the coolant is changed at least every 5 years or 50k miles.

Don't forget about the cooling supplement tabs, which could help prevent head gaskets being eaten away by the coolant.

Don't forget about the cooling supplement tabs, which could help prevent head gaskets being eaten away by the coolant.

Yes, good point! They are required to be used on all GM aluminum engines.

I thought the big reason to change coolant (I was told every 2 years with my 4.9 eldo.) was the 4 point motors had aluminium block with cast iron
heads and cast iron cylinder sleeves ,also the pellets were to seal any voids with mating of the different metals,I've never heard of pellets being used as the reason for protection of head gaskets. learned this from my local caddy club.

I thought the big reason to change coolant (I was told every 2 years with my 4.9 eldo.) was the 4 point motors had aluminium block with cast iron
heads and cast iron cylinder sleeves ,also the pellets were to seal any voids with mating of the different metals,I've never heard of pellets being used as the reason for protection of head gaskets. learned this from my local caddy club.

Any and just about all aluminum motors, either with an aluminum block, or aluminum heads or both can have porosity problems. It's just the nature of aluminum. That's the reason that car manufacturers require the use of a sealer in the coolant to prevent small porous leaks.
And yes, changing the green coolant in your 4.9 every two years and adding the sealant tabs is the best way to go! How many miles on your 4.9?

I thought the big reason to change coolant (I was told every 2 years with my 4.9 eldo.) was the 4 point motors had aluminium block with cast iron
heads and cast iron cylinder sleeves ,also the pellets were to seal any voids with mating of the different metals,I've never heard of pellets being used as the reason for protection of head gaskets. learned this from my local caddy club.

If you read the ingredients of the pellets, you'll find it contains ground up walnut shells. That acts like an abrasive that helps keep the seals cleaned from the corrosive effects of the antifreeze. The ground up ginger root in it is what seals tiny leaks.