Again, there is an upper limit on possible values. In LTE, the initial TA sent from the BS to the UE is an 11 bit quantity, restricted to a maximum value of 1282 (incremental updates sent from the BS to the UE are signed quantities packed into six bits). This provides for a maximum (one-way) distance of just over 100 km.
Cellular Repeater Antennas, LTE and Timing Advance