I had my basals down in a week, but being a long term CGMS user I had a pretty good idea what I’d need when I began, and with a tweak from my trainer was good to go very quickly. My I:C ratios actually needed much more adjustment, as I was not previously using long acting insulin during the day, so having a steady daytime basal rate at all was a bit of a switch.
One more thing I would like to add. For us, bolus insulin needs (ICRs) remain relatively stable until there is a significant basal change. For my niece it is the basal insulin that constantly changes due to growth hormones and I guess preteen hormones, monthly issues most woman have. And the basal insulin only significantly changes in the late afternoon to 1 or 2am hours. I hope your ICRs are likewise stable, once you do establish what they are. And you will probably see an overall pattern of your own once a year or two goes by. I was also told by CDEs and trainers that if you are running high and you don’t know if it is basal or bolus to change the Insulin to Carb ratio FIRST. Then you can ascertain if it is bolus, basal or both. Since she change so often, if high, immediately change the ICR up. Then figure it out from there. We could not possibly basal test each time she has an issue because she has issues three times a week at this age. By changing the ICR, you can get a pretty good idea. Of course, you must test two hours after eating when you do this. I have learned, through trial and error it is almost always her basal insulin that needs changing. I don’t think this is the norm; maybe the norm for this teenage age group.