It depends really on night length and nap length. Some LOs do a long night, some not. Some do 1.5hr naps some don't...
An A time of 1.5hrs with 3hr E and 1.5hr naps would get you through the day on 3 proper naps and CN if LO does a 12 hr night. Could be around 3 months but it really depends on the LO, could be earlier. Some younger might be doing 3 naps without a CN and a longer night so the A time might be less than 1hr 30, or the nap longer than 1.5hr.
At 4 months or around then A time is 2hrs or more and if naps are 2hrs then 2 proper naps and a CN get through the day. But some 4 month olds short nap developmentally and do four or five 40 min naps a day.
Clear as mud