I have been using Adobe Experience Manager for about a year.

I have been using it for nine years now. 

I've been using Adobe Experience Manager for more than five years.

I have been using Adobe Experience Manager for more than a couple of years.

I started using this solution in 2013, so I've been working with it for nine years now.

I have used this solution for three years.

Over five years.

I have used this solution for three years.

I've used it for the past three years.

One to three years.

I have used this solution for around four years.

I have been using this product for the past six years.