I have been using it for one and a half years. 

I have been working with Apache NiFi for one year. 

I have been using the solution for five years. 

I have been using this solution for a year.

I have been using the solution for two years. I am using the version that was released before the latest version.

I've used it for two months.

I have been working with Apache NiFi for a year and a half.

I have used this solution for more than one years.

I have been using this solution for one year. 

We have been using Apache NiFi for between five and six years.