That depends on what your goal is.
Part time income?
Full time income?
Just sharing the love of your hobby regardless of income?
Something else entirely?
Each one of those will result in a different answer as to how many pages you should strive for.
Back when I first joined (2013), I was wondering the same question and searched the forum to see if anyone had asked. At the time I had found a few threads on the topic and the general answers being given had all said "you need a minimum of 1,000 pages to succeed" or "you need to make one page a day for 3 years before you'll start seeing a profit" (which is 1,095 pages.)
As of today my site is now almost 4 years old and at 1,368 (pubic access) pages (and 3,000+ that are private/password access). While it brings in some income, I would not call it enough to pass for a part time job. As my goal was not for it to be a full time income, that's not an issue for me, but it might be an issue for someone whose goals ARE to have their site be a full-time income.
Than again, I started my SBI site August 2013 and didn't start to monetize it until January 2017, more then 3 years later...so while it's been out there, it hasn't been given a chance to see what income potential it had all that time.
But while most people were answering "1,000 pages before seeing a profit" or "3 years of a page a day before seeing a profit" I've seen people on here with answers all over the place. I remember one women was living full time off her SBI site after only 21 pages and another had mentioned having close to 6,000 pages but was struggling to see any traffic, let alone income.
Have you ever been to that list of the top SBI sites? The list that includes the Birthday Party site, the Australia site and all those... go have a look at each of those sites.... they have THOUSANDS of pages - THOUSANDS - one of them has over 10,000 pages. That's why they are making such huge incomes. Those sites are truly massive. And every one of them says they post at minimum a new page every single day and strive for at least 3 to 5 pages a day and have done so for 10+ years. 10 years of 1 page a day is 3,650 - 5 pages a day is 18,250 pages after 10 years.
Think about it - if a site with 10k pages gets only 1 visit per page per day, that's 10k page views a day on the site as a whole, and most topics can expect at least 10 views per page per day meaning those sites are getting around 100k visits a day MINIMUM just because of the sheer huge amount of pages they have.
I think that's the logic behind the common answer of "strive for 1,000 pages" because, if you have a 1,000 you are pretty much guaranteed a minimum of 1,000 pages views per day on your site, even if the topic is not popular. Having 1,000 pages allows you to "succeed" in a topic even if the topic has no popularity at all.
No clue how many sites around here have 1k+ pages, but I know when I visited each of the sites SBI has listed as their top earners (the ones buying houses and cars off their SBI income) when I went and looked at their sites, they were all mega sized massively huge sites that had been online for 10 years or more and had waaaaay over 1,000 pages listed in their site indexes.
So, if you are looking for an income like those sites have, I'm thinking there must be truth to the logic of "3 years and 1,000 pages before seeing profit".
As I've just crossed 1,000 (public access) pages myself and have now also started monetizing my site, I suppose I shall soon see first hand if the "1,000 page" answer is true or not.
I think the answer is gonna be different for every site because of differences in popularity of certain topics.
I think the best thing is to write as many pages as you need to get your site topic's message out there, and try to ad at least 1 new page a week. If you want to do this as a full time career, I'd say add 1 new page a day minimum.
But how many pages you need total, seems to be dependent on the topic itself and really has no one size fits all answer.
Take my topic for example - it's super tiny, sub-niche. It's a hobby that has an estimated 7,000 participants world wide. Well, that means I'm going to struggle to get much traffic, because my topic has very low demand. But, I knew that before I even heard of SBI, so I already knew it'd be difficult to get traffic, long before I started researching to find a web host. (I'm an author and my topic is the small sub-genre, with-in a tiny sub-genre.)
For me, my goal was having a place where my (already established) fans could have a place to access my work. I had originally been posting on fan-fiction . net since the 1990s but they had a ToS change in 2012, so I suddenly had 20 years of stories that were no longer allowed on their site and had to find someplace else to post them.
At the same time my original web host for my previous author home page was having server crashing issues, so I just decided to solve both problems by moving everything off both sites to one consolidated site, and thus ended up on SBI.
So, when I joined SBI, my goal was to find a web host that could deal with moving 9,772 pages (I still have a long ways to go before they are all moved over to SBI) off of multiple other sites (including 32 blogs) all to one server without having to worry about band-width issues or server downtime.
Thinking about SBI in terms of using it as a business/income was not a deciding factor for me because my goals for needing a web host was a heavy duty server that could handle huge websites.
So, all lot depends too on if your goal is using SBI as an income or not as well. As every one has different goals (and not every one starts a site with a goal of in being an income) that also ends up meaning, how many pages you need to reach your personal goal is going to vary depending on your goals.
My personal feeling is that the best topic is always the topic you would be happy to write a new page for every day for the rest of your life, even if you never made a penny at it.
When you find THAT topic (your heart's true passion) then that's the site topic that best fits you and ultimately will be the one that brings in the most income for you, because it's the one you'll be driven to put the most hard work into.