So far so good with the S8+. I haven't actually kept track too closely but I think I've been getting them monthly, though several days after folks here on other carriers mention getting their updates. The only one they were infuriatingly slow with was the patch to fix the pink screen problem. That was a few weeks later than other carriers put theirs out, if I remember correctly.Another AT&T user? How's their update schedule normally? First Android phone I've had on the network.
AT&T and Samsung did pretty well with my S7 Edge.
My unlocked S7 that I got directly from Samsung was horrible. Samsung ignored it until they were trying to lure angry customers over to the S8.
Nothing Samsung and AT&T do will ever compare to how fast the updates come to Google phones and to my unlocked HTC when I was running it.