It has been in my company for around 15 years. 

I have used the solution for ten years.

I've been using this solution for two years. 

I've been working with Tivoli NetCool for about five years.

I have been using IBM Tivoli NetCool for around seven years. 

I have been using IBM Tivoli NetCool since 2006.

I have been selling IBM Tivoli Netcool for three years.

I've been using the solution for five or six years. However, I only really manage it if someone from that department is going on vacation. I don't have much experience, but still, I can do some basic troubleshooting. 

We have been using the product for approximately 13 years now.  

I've been using the solution for a while at this point. It's been about five years or so.