How long will it last?

i read a guide on how to hook a lcd to a printer port and im wondering how long would it last with the information on this guide and i know that i should get the usb/serial lcd but it is out of my price range and i love to solder :) heres a link to the guide i read
i see in some guides you need pots why is that?
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CF Tech

First, a word of warning on the ModdersHQ guide: It does not have a current limiting resistor for the backlight, and will most certainly damage the backlight of any LCD connected to it.

Lifetime will probably be limited by the backlights. Yellow/green, green and red have about 50,000 to 100,000 hour lifetimes (5-10 years). Blue & white are more like 10,000 hours (1 year) at full brightness. You can shorten the backlight's lifetime drastically if you do not have a current limiting resistor in place. Read and understand this thread before you continue:

The pots are used for contrast setting and backlight dimming. Take a look at this post:

It has some links to guides.