You’re right, it depends. What I can tell you is that the USPTO currently has around 800,000 applications in their backlog and only about 8000 examiners. That’s 100 applications per examiner, and we all know how time consuming reading a patent really is, even more so when examining it. Plus, every application requires certain steps, which could also slow down the process.
Right now, it takes roughly 2 years to get your first Office Action from the USPTO. However, it highly depends on the field that your invention fits into: the more crowded, the longer it takes. For example, if your invention is in a very popular field like computer software, it could take twice as long. But if it’s in a less popular art you could even get it in 1 year.
Also keep in mind that every application gets about 3 office actions before getting the patent, and you need to respond to each of them, thus requiring more time. So all in all, you could get your patent in about 3 years if you’re lucky. That would be the minimum.
You’ll have to be patient and keep pushing forward.