I use these in two different bikes. One is a gravel bike running Holowtech II cranks, the other is a MTB with a GXP crankset (so the bearing only fits one side).  The durability and hardness of the bearing is really great.  If I keep an eye on keeping the seals free of grit and water intrusion, I get 5000+ miles of trouble-free performance.  These come pre-packed with a lithium-based grease which I like, as it is more resistant to "bleeding" from high pressures and high-torques applied.  It seems the lithium does a better job of repelling water/dirt than other greases.  If you have a steady hand, the seals can be carefully removed and reinstalled for grease repacking.  But at the great price for these, and the super low cost-per-mile of running these bearings, one wonders why you'd bother.