I've been using this solution for 10 years. 

I have been using Zimbra Collaboration for four years. My company is a vendor and reseller of Zimbra.

I've been using Zimbra Collaboration for about three years.

I have been using this solution for six years.

We have been using Zimbra Collaboration for two years.

I have been working with the solution for more than ten years. 

I've been using the solution for five years. 

I've been using Zimbra Collaboration since 2011.

I have been using Zimbra Collaboration for approximately seven years.

I have been using the solution for two years.

I am using the solution currently.

I’ve used the solution for three to five years at this point. I’ve used it for a while now. It’s been a long time.

I have been using Zimbra Collaboration for almost six years.

I have been using Zimbra Collaboration for nearly two years.

I have been working with Zimbra Collaboration for the past three or four years.

I’ve been using Zimbra for more than 4 years.

I've been working with the solution for two years at this point. It hasn't been too long.

I have been using Zimbra Collaboration for approximately 10 years.

I have been using the solution for a couple of years.

I have been using Zimbra Collaboration for approximately two years.

We've been using Zimbra for about four or five years.

I have been using this solution for approximately nine years.

We’ve used Zimbra for 4 years.

I have been using Zimbra Collaboration for approximately six years.

I have used it for a few months.