Hi there,
Great responses so far. I just wanted to add that my DS is near nine months old and I tried to drop the catnap around 7.5 months. I ended up with a very tired baby which caused poor night sleep, waking several times, sometimes every hour. I reintroduced it for a couple of weeks to improve night sleep and now we're back to phasing it out.
Like Aarismom said, some days you will need it, other days not. It often depends on how long their first two naps are and when the second one ends. If my DS sleeps past 2:30 for his second nap then I can stretch him to bed of 6-6:30, otherwise he gets a short nap around 4:30-5:00 and his bedtime is closer to 7:30. I find now he sleeps best at night with the no catnap day...but it has been a very rough time sorting this out.
take it day by day...good luck!