When did you know it was time to drop the 3rd nap?

We've got a 7 month old boy at home, and after being touch and go with naps at first, he's become a good napper and a good night time sleeper. He usually does two 75 minute naps, and 30 minute nap (usually in that order, but sometimes the short nap is the first or second one).

We've been reading that around the 9-10 month range, babies can drop the 3rd nap as they get used to longer naps during the day. But this week, he's been *really* fighting the third nap, and yesterday he didn't have his third nap at all and ended up having to go to bed early (he did sleep nearly 11 hours straight, but that meant waking up at 6:00 a.m. instead of his usual 7 a.m.).

So, it seems a bit early at 7 months, and he's not necessarily napping longer yet with his other naps, but does it seem to you that it's time for us to drop the 3rd nap? How did you know when was the right time for your child?

Let me know!