I have been working with this solution for about 15 years. I worked at British Aerospace Engineering for five years, and defense always uses DOORS. It's part of the government contract, they mandate that you use DOORS for your requirements management. I recently left British Aerospace Engineering to work for CNH Industrial. CNH Industrial uses Polarion, but I'm the lead systems engineer for all requirements, development, and management, and we're going to migrate to DOORS.

I have been working with IBM Rational DOORS Next Generation for five years.

I have been using IBM Rational DOORS Next Generation for five years. I use the solution's latest version.

I've used the solution for years. I've used it for quite some time. 

I've been using this solution for six years.

I've been using the solution for two years but not on a daily basis.

I have been using the product for two years. 

I've used it for five years.

I have been using this product for about four and a half years.

I've used it for three years.