New membrane is never a bad idea, but it would be to your advantage to find out more about how to use your specific system, particularly the flush feature, as that's a major factor in aiding a longer life for your membrane. Must be some instructions available from a company like Vertex? Would also help if you provided more details on your unit other than Vertex Puratek. How many stages, including pre filters & carbon etc? What micron value are the prefilters & how often do you change those?

Aside from that, depending on your source water TDS, your membrane may last longer than other people's or not. Folks on the west coast generally have very soft, low TDS tap water to start with so their membranes can last a very long time because they're not dealing with 100 - 200 or even higher TDS tap water. Nevertheless, even with an average 180 TDS tap water here, I'm still on my first membrane after 5 years of use. I manually flush before & after each run & I generally make a minimum of 14 gallons of water.

I've found the Buckeye Field Supply (now Buckeye Hydro) site a great source of info as well. Never steered me wrong & they're happy to help even without making a sale. Link to their FAQ page:

http://www.buckeyehydro.com/faq/

Some great info there on tools such as pressure gauges to aid in determining when it's time to change various filter stages, including membrane.

Have you confirmed that your water utility uses chloramine? If not, adding another carbon stage will not be required and will only slow down production needlessly. You should be able to contact your utility, city or whatever web site to find out what your water is treated with. They are legally required to make water quality reports public. Always a good idea to find out exactly what you're dealing with when putting together a filtration system, that way you know what you do or do not need.