That seems really long, and it is pretty rare to actually have a winch cable - normally it is a strap.
Typically you wouldn't be hooking up your winch strap with more than 3 or 4 feet out unless you are really shallow launching a roller trailer
My strap only gets pulled out about 6 feet at the most, I think my strap is 25 feet long. The first couple of feet of the strap often gets worn/faded and what I do is cut off the bad section and resew the hook and I basically have a new strap again.
..... You wouldn't spool a fishing reel with only the amount that matched the distance of a cast.
I would caution that a cable or strap any longer than necessary only increases the effort required to crank the boat in due to the increase in pulley diameter. With a nearly empty pulley you have quite an advantage on the load. As the pulley diameter increases, that advantage decreases, possibly leaving you grunting unnecessarily in some situations.
My vote would be no longer than required to reach the back of the trailer at maximum.