Win10, 64bit, Nvidia GeForce 840M, all up to date
Effect of force field on hair-system stops at frame 100
Open attached blend file and playback animation (Strg-A).
Till frame 100 the hairs are driven apart by the force-field, then the effect stops and the hairs falls down.
Hair - Force Field.blend
Force field on external object (empty in scene) works over all frames.
But second bug(?):
if before mentioned bug has been tried out, the force field on the empty is not taken into account, even if cache is cleared, rebaked... (red line in time line stays).
Only changing particle number i.e. from 100 to 101 and back to 100 clears the "cache"-red-line and then the empty-force-field pushes the hairs.