Links are valid forever, unless a question is deleted. The link you posted from reddit, points to:
/q/25/255 and it actually makes sense because the poster asks if this is related to twitter (i.e., is
/q/25 related to
/q/25/255 basicly means question with id 25 referred by user with id 255. The important part is the
q and the
25. The part that comes after the slash can be basicly anything,
/q/25/i-like-popcorn is also a valid link and will always open the question 25.
When questions are closed, are existing questions renumbered, thereby harming accuracy of short links referencing question numbers?
No, IDs wont change never.
I am working on the StackMonero Twitter bot and desire stable links. Should I be using this short format or this long one? My preference is for the short link format but not at the expense of stability.
http://meta.monero.stackexchange.com/q/45 - everything after that is optional, like:
By the way, I'm running one of the ethereum twitter bots, if you have any additional questions.