Timken bearings...when would you repack?

I don't have a lot of luck finding "Timken" bearings any more. I put off packing my trailer until about seven years had elapsed. I always check for heat at each stop and had no issues. However, I did note that when I checked the bearings, three of the outside ones had small pits, which I replaced. This would probably not been an issue, but I felt safer changing them, especially since they are relatively inexpensive. Some of the races that I've obtained locally will not fit the hubs, and I've found the ones obtained directly from Lippert work fine.