Barrel life of 1500 rounds but 3500 rounds shot.
If using Excalibur, PGKs and other terminally guided rounds does the "1500" number still hold water?
I presume there are two effects of wear - accuracy and durability. Do PGMs extend the life of the barrels - assuming similar charges?
First of, barrel life for artillery is not measured in "rounds" but in "effective full charge" rounds. Only a round fired with the highest charge possible would you count it as 1 x EFC. If you fire at lower charges, then they only count as varying fractions of 1 EFC so it's usual to fire many more than 1,500 rounds and still not reach 1,500 EFC.
Second, firing rounds creates two things, wear on the barrel and possibly stress fractures in the barrel. Wear increases the diameter of the barrel in a way that ends up reducing muzzle velocity and thereby range and accuracy. Range can be compensated for. Canadian guns have small radar sets that measure the muzzle velocity of each round fired and thus allowing for adjustments to the range.
As guns approach their effective life they are generally bore scoped and receive other tests to determine if there is excessive wear or other damage to the barrel. If not the EFC life of the barrel can be increased. Whether or not a barrel is condemned or not is a risk assessment. One can continue to adjust for muzzle velocity but barrel cracks and fractures can lead to a catastrophic barrel failure and that risk might be acceptable during a war when it wouldn't be in peacetime. There's more to it than just this and this article
explains some of that.
Firing a precision munition does not "extend the life of the barrel". A precision round results in an EFC, or a fractional EFC, just like an ordinary round depending on the charge fired. On the other hand, with the muzzle velocity adjusted for and the round being guided, the precision rounds accuracy is not effected as that of a "dumb" round fired from the same barrel would be.
Note too that sometimes the nature of the ammunition makes a big difference to the barrel wear as well. Back in the early 2000's Canada had produced 105mm rounds with a driving band that seriously eroded barrels far beyond what had been normal.