I started using the solution this year.

I have been using Visual Studio Team System for fifteen years. Also, I am using the solution's latest version.

I have been using the product for three to four years. 

I have been using the solution for less than a year.

I have been working with the system for 15 years. 

I've been using the solution over the last 12 months. I've used it for a while.

I have been working with this solution for about seven years.

I've been using that software for approximately six years.

I have been using Visual Studio Team System for approximately 10 years.

I have been using the 2015 edition for some four years. I started using the 2017 version more recently, perhaps four or five months ago.

I have been using the solution for two years. 

We have been using Visual Studio Team System for the last five years.

I have been using Visual Studio Team System for more than ten years now.