Suspension leak issue

Hi Folks,
I took my 2012 4WD for service recently. When I went to pick it up, they told me that everything looks good except that the front suspension on the driver side is leaking. I asked the guy what he meant by that, and his more elaborate explanation was that there is some liquid inside the suspension and I have somehow damaged the suspension probably by taking the truck on a rough road. He then said that in a few months I am going to have to replace the suspension with a new one.

I asked if there is something I can do to maintain and prolong the life of the suspension, but the informed gentleman insisted that there is nothing I can do but to replace it when it is time.

I was hoping someone here could explain to me a bit about what this problem is exactly, is it common issue with Tacoma? What are the symptoms, and is there really nothing I can do to make the suspension last longer?

I have Firestone airbags installed on the rear suspension. If I end up having to replace the front suspension, is there any setup that you would recommend that would perform well (much better than the OEM) on rough roads that I take occasionally to hit up those trout lakes around here.