4wd indication blinking?

While traveling to Washington in my 1999 Explorer 4.0 the other day, I was cruising alone at 80 mph & the 4wd & 4wd low indication lights in the dash blinked 5 or 6 times then went out.
This went on several times during the trip.
Is this something I should be concerned with? or is this one of those many ( Oh. its a Ford & it does that ) kinda things??
The truck ran great.. No other problems other than the indication lights blinking all throughout the trip.
Again its a 1999 Explorer with the 4.0 and 86,000 miles
any & all input welcome.. Thanks