Cracked spoke holes
I noticed that 6 spoke holes of the 28-spoke rear wheel had cracks. All on the drive-side - meaning 6/14 drive-side spoke holes were cracked (over 40%). The rim is a Bontrager TLR that came with my Trek Checkpoint ALR 5 with disc brakes. I had not adjusted the spoke tension since buying it and use the bike mainly for highway commuting.
From what I've read, spokes of disc brake wheels experience much more tension during braking than rim brakes. The rim is only 4 years old. To me, that seems like a short time for rims to be cracking. Would this be considered just normal wear&tear? What is the average mileage lifespan of disc-brake rims? I just assumed that they would last longer than rim-brake rims due to lack of wear. I hadn't considered spoke tension being transmitted from hub.
Thanks.