30-90days seem absurd to me.
Not sure why you think this amount of buffer is absurd. For most applicants who have kept perfect records, waiting thirty to ninety days to apply after reaching the minimum should give them plenty of margin, a good buffer, not at all absurd. Indeed, as a few others report, even 20 or 30 days can be enough.
But an applicant who accurately reports all the relevant information in the application and presence calculation should feel confident that when a total stranger bureaucrat reviews the presence calculation an extra 30 to 90 days should easily help the processing agent and citizenship officer feel comfortable in concluding the applicant met the requirement without sending the application into non-routine processing to obtain further evidence documenting presence.
But sure, some applicants will be prudent to wait longer. Depending on a range of factors. You've shared way, way too little about your facts to know whether, say, 90 days would be plenty for you, but 90 days would easily pass the NOT-Absurd threshold. And, depending, maybe even just thirty days passes the NOT-absurd threshold.
One of the more common mistakes prospective applicants make is to focus too exclusively on the number of days present and overlook other factors which should be considered in deciding WHEN is the best time to apply. For example, I was self-employed, my work-product sold to clients abroad, so in conjunction with some other personal circumstances I elected to wait a lot longer than an extra 90 days. But that was about my personal circumstances.
Many, many times waiting longer to apply can and does mean the oath of citizenship comes sooner. Obviously, not always. But waiting another thirty or fifty days goes by really fast for most, and then when for months and months they do not hear anything about how the application is going, which is very common these days, there is NO worry that some stranger bureaucrat is not comfortable feeling certain the minimum presence requirement is met.
Note: 1095 days credit meets the requirement. That gets the applicant to the oath EVENTUALLY. In contrast, having a buffer is mostly about two things:
-- one, is having enough days just in case there was a mistake, OR A STRANGER BUREAUCRAT SUSPECTS A MISTAKE, so that even if some days are deducted the applicant is still eligible
-- two, just as importantly in my view, is having enough days the total stranger bureaucrats reviewing the application are easily persuaded there is NO reason to question or doubt that the applicant meets the requirements, no need to make further inquiry into evidence of presence
The first of these is about being sure to be eligible. There is a tendency to focus on this alone. Which works out for many. The second is about approaching the process to minimize the risk IRCC perceives a need to dig a little or a lot deeper, about reassuring the citizenship officer there is no doubt about meeting the presence requirement. More than a few overlook or ignore this aspect. Still works out OK for some. But this forum is rife with tales of woe from applicants complaining about how the process is taking longer for them than it is for others. Contrary to much of the whining, it is NOT about arbitrary or capricious or malicious or neglectful processing agents. There is never any way to guarantee an applicant will benefit from the fastest, smooth sailing path, but there are plenty of ways to increase the risk of delays and non-routine processing.