This got super spammy in the end, or as I entered the last era. I had sort of stopped trying to maximize the number of Aikens quite some time ago. So much new land to conquer etc and then it was somewhat less important somehow. But in the last era there was 72 notifications.I agree to spam, but I haven't found any better yet. I don't know how to compact the messages.
In the first era or two I think it's nice and relevant to show which tiles are gaining the +1. This is a time when yields per tile still matter and and there are choices on what tiles to work. But in the last couple of eras the gain by itself is relevant but knowing exactly which tile gets it is not as more or less every tile that can be worked is going to be worked either way. I would really settle for the summary option then of saying you gained X of this and that and the other.
If it is possible perhaps one could modify or change the routine that does this checking to also first check which era it is and then displaying different once depending on the result, so if it's the first couple of eras then do the by the tile display as it is now but in the later eras switch to the summary option. One could have a summary in the first ages to just to show a summary, even tho perhaps then check the number of Aikens first as it's kind of pointless to display a summary if there are very few Aikens around. Some breakpoint might be needed. Around 10 or so perhaps might be relevant, smaller then that just display the normal amount and the summary doesn't matter much.
That said this could also be a map size and game speed (I only really do huge or large maps on marathon) option, after all larger maps tend to be more cities which should be or equal more Aikens. So I guess if you have a small(er) map or for some reason doesn't have a lot of Aikens even in later eras then perhaps a tile by tile option is nice to have then to. It's just clicking away 70+ info bubbles isn't exactly fun (I know I don't have to click them away but I sort of do since I tend to check up on all the notifications every turn to see what was happening or what was gained etc).