Some women begin taking hormones in the Recovery Room; others have to wait until months after their hyst to give endometriosis a chance to die back. Some doctors see no reason not to start you on HRT as soon as your ovaries leave your body and others prefer to wait until your endogenous levels fall back enough that you are showing symptoms of deficit, rather than have you risk too high a level while you use up stored hormones from before your surgery. Whatever your doctor's favored approach may be, unless there is a compelling health-related reason why you cannot, you should be able to start hormones as soon as you begin to feel a need for them. If your doctor told you "I want to wait till your 6-week checkup to start you on HRT" and by week three you are a basket case, don't wait: call and let that doc know that you're ready now. You shouldn't have to "earn" your hrt by the depths of your suffering while waiting out some arbitrary timeline just so the doctor can justify that they're needed.
No one knows how long it will take to use up all of your stored pre-operative hormones and everyone's rate of consumption is individual and different. Nonetheless, it's a safe bet to predict that the first three months or so after your surgery are going to be a time of transition. Since this period also coincides with your major healing work plus the elimination of all the chemicals you took in during and immediately after surgery plus the recovery from all the stresses of surgery, it's a toss-up just what might be causing any of the many symptoms you may experience during this time. With so much going on at once, nothing happens in a smooth curve, least of all the drop off of your own hormones and the switch-over to reliance on exogenous (from outside the body) dosing.
Your first dose amount is likely to be a "usual starting dose" or that dose modified by your doctor's best guess. If you are younger rather than older, your dose is going to be on the higher side: a woman of 30 will probably take a higher hormone level to feel good than a woman of 50. If you are heavy, your dose may be lower than a skinny woman's, although a great big gal will clearly need a higher dose than a tiny one if both have the same proportion of body fat. A smoker will need a higher dose than a non-smoker whereas a regular drinker may need a lower dose than a non-drinker. These are some of the things your doctor will take into account. There is no "right" dose to start at—just a reasonable place to begin.
Because this is a time of fluctuation, you can expect that the dose on which you begin will not be the one that you'll need once you are recovered and have used up your endogenous (from your own body) stores. A correct dose at first will most typically become too low over time; starting with the dose you'll be on eventually may give you uncomfortable symptoms of excess at first. This does not mean that you "habituate" to hormones or that they "stop working." This is a popular myth, but one that demonstrates misunderstanding of how the balancing process works. If a dose that was okay stops being right, it only means that your background needs have changed or the process of adjusting to a change has ended and the dose you were taking before no longer meets your needs.
So how do you get balanced during those first few months? You don't, really. You take your doctor's best guess and you tune it as best you can for the moment. Beyond that you can only try to accept with equanimity the fact that it is a dynamic situation and you aren't going to be able to do more than try to hold your own. This doesn't mean you need to put up with being miserable—you should never do that—but it does mean that you need to recognize the transitory nature of this period of your recovery and recognize the limitations of HRT in keeping up. By the second half of your post-op year, assuming you've identified an effective HRT for your own body, things will be settling down (although one more tweak is fairly common as we settle in further) and you will find that you can go much longer spells without even thinking about your hormones.
