depends how many you want to install... 2 more would be less than 10 amps, which even at idle would not be a problem IMO.
then the alternator will certainly not have a problem!It would only be the two extra. They would be driving with pencil beams. The high beam have too much scatter for me. My highlander had higher lights so it makes seeing out farther easier.
I live in NY and work up in MA, I do about 275 in miles one way each week.