Replacing Les Paul 490/498 stock pickups

[nestle]

+1 for the SD 59's they are nice.
But I have a newer LP standard with the burstbuckers and I really like them a lot. They are very well balanced and musical yet just enough bite and sparkle, I think they are also a great choice.

[anambrose]

+1 for Duncans 59 bridge and Jazz in the neck a good match; JB bridge and Jazz neck is also a good combo for reasons already said. I have a couple of guitars with Classic 57's that use alnico II and they're muddier in the bottom than alnico V. So a 335 with Classic 57's is okay as the laminate maple body and center block tends to thin it out a bit. I have an LP with Burstbucker Pro's which are alnico V and I love the way they sound more chime on top and upper mid and tighter bottom end overall better string to string definition. These guitars came with those pickups and as they do what they do fine I wouldn't change the PU's out. If I had a guitar that had PU's I didn't like the sound of I would go to the Duncans. I've even used an ESP 7 string with a stop tail that had Duncan Designed PU's I found for $200 on ebay. Curious as to what type of Duncan US PU's they were modeled after and it was JB Bridge and Jazz neck.

[calaverasgrandes]

I suppose I will regret opening this can of worms but here goes.
Magnets lose a bit o strength as they age. they also are affected by heat. Though not sure if human body heat, even from a suffocating hot show, is warm enough.
Either way as magnets lose their field stength ovr time I would be surprised if they did so in a linear fashion. So I am pretty sure that older pickups are gonna sound different, not just because of Alnico/ceramic etc, but also from the age of the magnets.
just saying is all.