Hi
Most 8-9 month olds are on 2 naps per day (some still are having a catnap as well). Length varies, from probably 1 hr per nap, to 2 hrs per nap. A times vary too, from 2 hrs right through to close to 4 hrs.
My lo is on about 3hr A time, and 2 naps of 1.5 - 2 hrs each when we are at home. At daycare, longer A times shorter naps.
On days home her routine is
6/6:30 wakeup
9ish 1st nap
1ish 2nd nap
7/7:30 bedtime
But we watch cues more than anything, rather than times. Today has been
6:30 wakeup
8:30 nap - 1.5 hrs (bad night, and teething really bad, so tired early)
12:30 nap - 1.5 hrs
We ahve a rule in this house that cranky babies go to bed, and she has been whining all her A times, so they are short today for mummy's sake
So I have yet to decide how we will get her to a 7/7:30 bedtime. I may offer another nap, although she has never taken to catnaps. Or I may go for complete distraction and take her swimming at the pool (her favourite activity).
HTH