The Dutchman stated when he arrived at Old Trafford in July that he should be judged three months into his tenure with the Premier League side.
Van Gaal conceded last month that he was "stupid" to come out with the aforementioned remark as he got to grips with the size of the task he has undertaken.
And with United sitting in mid-table in the top flight ahead of Saturday's clash with Crystal Palace, the former Netherlands coach has stressed the need for patience in what he views as a long-term project.
"We are in a process and that process shall take more than one year," he said. "It shall take three years.
"I cannot say when the results are coming. When I did it with Bayern Munich it was December 8. It can be February 1. But it doesn't matter. This is a process of three years. I have signed for three years.
"It takes a lot of time. But at the end, when they know it and they are doing the things with conscience, the results shall come.
"Our goal [this season] is to get back in the Champions League."
