When DS was 9 months old, he was down to 2 naps (and unfortunately he's making some moves to drop that second nap). He naps at 10 am and 2 pm (approximately, sometimes it's 10:30 and 2:30, etc.). He goes down for the night at 6:45 pm - 7:00 pm and is up for the day at 6:00 am. He usually takes one long nap and one shorter nap. If his first nap is 90 minutes or longer, the second one will be around 45 minutes. Sometimes those switch.
I'm a little surprised at 9 months that your LO is still taking 3 naps. Every baby is different, but my other friends who have LOs in that age range are also on 2 naps. As far as what to expect... at some point I'd try to consolidate his 3 naps into 2, which will eventually be down to 1 nap (though the age varies a lot for that).
I don't really understand people "frowning" upon the whole scheduling thing. I have always adhered to a schedule, but it's not like it's executed with military precision. Maybe their "you wait and see" attitude comes from the fact that, as LOs get older, they are a little more flexible with their scheduling needs, and sometimes will throw a wrench in the plan. I absolutely would not stress about LO going down for a nap at the exact same time everyday. Some days he's tired at 9:30 am, sometimes he's not tired until 10:30 am. At bedtime, sometimes he's tired by 6:15 pm, sometimes he's not tired until 7:00 pm. I'm flexible with it, because he's a kid, not a robot. We keep a somewhat straightforward schedule, but it allows for some adjustment based on how he is feeling.
When he was tiny (less than 4 months) I used to OBSESS about the schedule. It made me and everyone else nuts. Now I'm more realistic and calm about it. Do I ever keep him up until 8:30 or 9 pm? Absolutely not. But I know everything will be fine if he goes to sleep at 7:15 pm instead of 6:45 pm and eats lunch at 12:15 pm instead of 11:45 am.
FWIW, DS got really sick back in August. He ran a fever of 103-104+ for an entire week. His sleeping schedule was completely shot to sh!t. I was beyond panicked that all of the sleeping habits that we spent months and months cultivating would be gone. After he got better, it took him about a week, and he was back to STTN with no problems. So the moral of that story is that, they go through phases, nothing is forever, and just take it all in stride.