Depends on several factors. Your initial license will take longer since there are more steps required, but upgrades can be fairly quick. This is because initially they must assign you an FRN and get your account established in the ULS system for your first license, but that task has already been done for upgrades so those changes can be made fairly quickly.
It will also take longer for things to post during holidays and especially during governmental shutdowns, since nothing basically can happen during them. Weekends also can add a brief delay.
The biggest variable is the team that handles your testing. The ability to electronically file the results of their testing session is not wide spread so in many cases the results and documentation must be sent to the VEC (the organization that processes results for the VEs that handle the testing sessions) by physically mailing them in (yep, using snail mail). This can add lots of time to the process. If your VEC allows electronic filing and your team has been certified to file electronically, the process can be quite quick.
All of this assumes that there was no issue with your paperwork. If there is any problem with the necessary form(s) there may be a significant delay in processing since the paperwork must be returned, the error corrected, and the paperwork returned for reprocessing. This process is often pretty long since many VEs aren't used to having things returned to them for corrections and may not check for returns on a regular basis.
You can probably assume that your initial license will be posted in a week or two on average. Upgrades will be slightly shorter, but still may take time due to the time to mail the paperwork. If you're lucky and use a team that can electronically file, it could be quite quick. Just a few days for the initial license and perhaps just a single day for upgrades.
For example, the testing team I did my last upgrade with was one of the first to be certified for electronic filing. They handle multiple testing sessions each month and are local to the VEC's main office so they were able to quickly and easily work through any issues hammering down the electronic filing process. I took my upgrade test and got my results around 7 PM on a Thursday. My results were in the ULS when I first checked around 3 PM on Friday (it might have been there much earlier, but since I didn't check earlier I have no way of knowing). For me, it was 20 hours or less from the end of my test to my upgrade being in the FCC ULS system.