Haven block rewards will never drop to zero. Block rewards will gradually drop until tail emission commences sometime in early 2026. At this point, rewards will be fixed at 0.6 XHV per block.
Miners need an incentive to mine. Because of the dynamic blocksize, competition between miners will cause fees to decrease. If mining is not profitable due to a high cost and low reward, miners lose their incentive and will stop mining, reducing the security of the network.
With Haven it is possible that miners weill be rewarded with the conversion fees from xAsset conversions. This will help offset lower block rewards and secure the network by offering greater incentives for miners to remain in Haven.
Tail emission ensures that a dynamic block size and fee market can develop.