geohaneke,
It is true that as of July, Nevada now recognizes the Texas LTC.
To answer your original question, each state has their own laws to determine if they will recognize non-resident carry permits as well as if you can possess permits from multiple states. For instance, Texas recognizes non-resident carry permits where as some states like Florida do not recognize non-resident carry permits. Also, Texas does not require you to surrender another permit when you get your LTC, so there is no problem possessing multiple permits.