i don't have a large sample size so i had to think about this one a lot, but thinking about it, the act of writing itself with no context attached to it is quite fast, if i start a draft i can slam out a good 1~2k words to start off with in a few hours. after that i slow down and chill out. it depends, either i write a few sentences each day or i get struck with inspiration and write a lot in one sitting. either way, if i get hit with some kind of spark, i can write a lot.
however i'm the kind of person who after a few days of squeezing blood from a stone stops... i just leave stuff alone, not sure if i'll ever finish it. this does help whenever i wanna go back to it cuz i can look at it with refreshed eyes. sometimes it'll be a while until i write, i'll read it over and over after leaving it alone for a considerable amount of time. this could be weeks. and then suddenly some time later i wake up from a daze and i had finished something up (this happened recently, it is genuinely a strange daze).
for example, i started the stay gold thing on july 21st according to google docs, i ended up finishing it off, editing and posting it on august 17th. i guess this could be about the average, i had a similar turnaround for the first chapter of long distance (similar length even).
i try to set a deadline, but it doesn't work! but at least i was like, i need to post the second chapter before july starts!! (i was able to in the nick of time, but it was scary)