I would guess that the reason your connection disappears is due to two reason:
1). 4 miles is a hell of a long way from the exchange
2). High contention ratios in the evening are probably killing your connection
The solution is to move nearer to the exchange (not practical) or switch to an ISP which is either operates from an exchange nearer to your home or which can guarantee lower contention ratios. Any ratio under 50 is acceptable.