My organization has been using the solution for the past three to four years.

I've used the solution for three years. 

I used it for the last five to six years. 

I have used the solution for four to five years.

I have been using Symantec Messaging Gateway for ten years.

I've been using Symantec Messaging Gateway for more than ten years.

I worked for the company that I'm working at now, for 19 years, however, I was gone for six years. In that 19 years, I had about 10 years where I was using Symantec Messaging Gateway. 

I have been using the solution for six years.

I have used Symantec Messaging Gateway for many years. 

I have been using the Symantec Messaging Gateway for about one and a half years.

I have been using Symantec Messaging Gateway for approximately three years.

We've been using the solution for two years.

I have been dealing with Symantec Messaging Gateway for about seven or eight years.

I've been using the solution for about ten years now. It's been a decade.

I have been using Symantec Email Security.cloud for almost two years. 

We have been using it for a month.

I have been using the solution for 1 year now.