Elections are typically triggered by one of two things:
Graduation out of Beta
The site grows to the point that it requires more attention than the existing moderation team can offer.
Each of these decisions are made by Stack Exchange staff, presumably with input from the community. There is no scheduled frequency.
It has been a while since Mi Yodeya ...
The Talmud (Sotah 22A) tells us that someone who makes Halachic Ruling based on the Mishnayot he learned destroys the world.
Rashi there explains that this is because he is making Halachic Ruling without having learned the reasons of the Halachot brought in the Mishna.
Yet we don't see anyone banning the learning of Mishna. I've never even seen a Book of ...
I can't speak for the other moderators, but when I'm facing obsolete flags on comments the first thing I do is pop open the deleted comments so I can see the flags in context. For me that's a one-click action because of a userscript I'm using; otherwise it's between one and three clicks depending on -- I kid you not -- window size.
If you delete your ...
That question1 was deleted by the community as being "rude or abusive". As the quasi-official description says:
The rude or abusive flag (formerly known as offensive) is meant to be used only in extreme cases, like hate speech, abuse against people, or abuse of the community or system.
For what it's worth, I agree with the community that this qualified.
Obsolescence can be hard to judge sometimes. We mods try not to delete still-relevant comments, but we might miss sometimes. This is particularly true if, as DoubleAA mentioned in a comment, a big long thread is being cleaned up. (Which usually comes to our attention via flags.)
Here's a scenario that has happened to me several times: big long comment ...
You can appeal either by:
bringing it up with the community here on Meta.
discussing it with the moderators either by flagging and explaining clearly your reasoning or asking (via flag or in chat) for a private chat room with them.
Feel free to double check others' decisions; deletions and closures have been reverted in the past.