I can't speak for everyone of course, but for me it's something like this:

Being evaluated as in what's the diagnosis I have took maybe a few weeks to a month or two with one session a week.
Being evaluated as in what are all the things that contribute to there being an issue took 2 years so far, but I'm not sure we're done with that. But that might be because I don't trust easily and take a long time to open up.
And evaluated to adjust or determine treatment, I'd that needs some statistics over a few weeks. Either T or I check in every few weeks about how everything is going and if something needs change, we change it.