How about some strategy & tactics?

[Mr Grumpy]

Fixed units can dig in
Improves defensive positions prior to a unit's release.

Also there are some units that when changing into travel mode lose movement points, so if you do this while they are still fixed (assuming they are out of the LOS of your opponent) will mean they will have full movement allowance on the move they are released.

How many times do you end up one hex short of where you needed to be on a particular turn...........