I need to write a longer piece on our approach at Oxide, but for us it takes effort (not always successful!) to hold ourselves to 9 conversations. This may (or perhaps does?) sound obscene, but (1) these are conversations not oral exams (we don't do red-black-trees-on-whiteboards), hopefully making them less stressful for the candidate (2) we take hiring really, really seriously and (3) I have learned from mistakes at past companies with grievous mishires, for which the downside is essentially unlimited. We have a front-loaded, writing-heavy process (we don't schedule conversations with anyone about whom we are less than enthusiastic), so for us, the conversations are an opportunity to really begin to explore what the dynamic with our potentially future colleague will look like. And time and time again, I have been appreciative of this broad approach: because different folks take such different paths in their conversations, it is not unusual for one person to see something that others either missed or didn't dig into -- and that becomes a serious concern. Of course, it also happens that one person has a concern that others have also looked at and feel has been addressed; we aren't necessarily seeking to build absolute consensus all of the time, but it's essential that we ferret out those concerns.
tl;dr: I think you have every right to ask a company what their process is, and when they can expect to be at a decision point -- but I think there are reasons (good reasons!) why companies may wish you to have many conversations before making a hiring decision.