We have two miles of fence-line to maintain. Originally, the DW would walk along with a 2 gallon hand-pump sprayer after I mowed as close as I could get with the bush-hog. She had to come back to the house to refill it about 50 times. It took her 3-1/2 days to get the whole fence. Eventually, we bought a little trailer to pull behind the lawn mower holding more water and round up. She would head out with the little sprayer, a jug of Round-up and two 5 gallon buckets of water. Then she could refill the sprayer several times while out in the field. That reduced the refill trips to the house down to about 10 times (except when the mower got stuck in a mud hole). It still took her 3 days. Then we upgraded to a 16 gallon 12volt sprayer. That roped me into driving the lawn mower while she sprayed. It still took 6 return trips to the house, but we got the fence done in 2 days. I kept telling her we needed to plan for old age. She's a real trooper, but I kept telling her we wouldn't be able to work this set up when we're 80. The DW finally agreed to get a 55 gallon, pto driven sprayer. Today, we got the whole fence in 3-1/2 hours. She still insisted on walking along to be sure everything was thoroughly sprayed around all the fence poles. But at least I got some seat time on the tractor. And, I didn't have to give up an entire weekend.
Plus, we can use it as a pressure washer to clean the eaves of the house, the travel trailer, or the tractor.
If it saves me a day and half every time we spray the fence, it will be well worth the money (about $500).