I've seen a couple mentions of watering every 7 days etc.
Try learning to "judge" when your roots/media are dried and water then. Lift the pot when fully saturated after watering and note the weight, it will be much lighter when dried out. If in doubt wait another day or two, even though Phals do like consistent moisture a drying will promote new root growth which is always a good thing. I totally agree with BigBill DO NOT use a heat mat under your phals, I grow mine in a greenhouse that dips to the low 50's daily and they love it.
One last thing on the browning air roots, this is probably due to low humidity which if growing on a windowsill not much you can do about it. Don't bother misting unless you plan on doing it hourly, and putting on trays of water is most likely not going to do anything significant to help either.
OK, rambling over
