I agree with NCperson, you want to avoid filling out a KY K4, if you can. If your employer withholds KY tax, you'll have to file a nonresident return for a refund every year. If they are unwilling to withhold PA tax, you'll have to make estimated payments to PA or have your spouse increase her PA withholding to cover you.
You said "The company mentioned I would need to visit KY some times in a year". That prompts the question: will you need to pay KY tax on your salary for those days. Yes, but "nobody" does. See http://money.cnn.com/2013/06/28/pf/taxes/business-traveler-tax-threat/
If your employer does withhold KY tax, then yes. You'll need to allocate days, when you file for a KY refund. PA will give you a credit for the little KY tax you end up paying.
