When to repot a Phalaenopsis

[orchidkilla]

Hello, as you probably guessed I'm posting on these forums because I need help with my orchid. I was looking at general guidelines as when to repot my Phalaenopsis, yet, I lack the experience to make an accurate judgment about my plant. I've gotten some conflicting advice and I'm wondering which is right:

Some websites say when the roots are climbing out of pot its time to change pots and/or media. Other sites say its fine for the roots to be climbing out of the pot.

History: I've had my moth orchid for about 5 weeks. About one week ago my orchid leaves started yellowing. My orchid is in a room with a south window and southwest window. My orchid has four large leaves, and the center leaf facing away from the south window, towards the southwest window is the most serious.

When I first got the orchid I took the orchid out of the larger pot and left only the plastic pot. I also took a look at the roots and most of the roots were green with a few almost brown roots. Since I've gotten the orchid the roots seem to have climbed or grown further out of the pot, while other root still wind around in the bottom. Now the roots not only are an inch or two above the pot but now are climbing out towards the spot between the south-west and south facing windows. The climbing roots are 5 inches long. None of the roots are poking through the holes at the bottom.

As for the flowers, the orchid was blooming with 3 flowers when I bought it from Costco. There is only one spike with 8 buds on the flower spike. I just noticed that the 6th bud is starting to open up. Yet, for about 5 days the first bud looks wilted.

Hard facts: one spike, 8 buds, six buds are flowering, one is wilting.
substrate: mixed bark
watering frequency: one a week with diluted fertilizer.
Pot diameter: 6 inches
largest leaf length: 10 inches
length of roots dangling over side of pot: 5 inches
temperature outside: low of 10F high of 50F and windy.
Inside temperature: 55F in day and 65F at night.

I'm not sure how bad my plant is, I looked for blacked leaf tip and black spots and found none. Is it good for my roots to be dangling five inches over the side of my pot? Should I panic now?