Do they have monthly rates for long-term campers and if so how much are they?

I believe Nebraska camping is camp in one spot for 14 days maximum and to my knowledge they do not give you a discount for staying a longer period of time. However some parks do offer winter rates when they do not have the water running I believe.

A Nebraska State Park Permit is required to enter this park area. A Nebraska Licensed Vehicle Park Entry Permit is $30 for an Annual Permit, $15 for a Duplicate Annual Permit (used for that second vehicle in your family) or a Daily Permit which is $6 per day you are staying.