As far as the toad front wheels are concerned, mile are miles whether towed or driven. The front end still hits potholes and maybe even gets dragged over the occasional curb, so the toad front end needs routine maintenance whether driven or towed. Most automotive gurus recommend regular alignment and balance check/adjust every year or 12,000 miles. Most of us stretch it out longer, but at the first sign of a problem such as yours, get thee to the shop for balance and alignment.
2004 American Tradition; 2013 Buick Verano
Homebase in the Ocala Nat'l Forest near Ocala, FL