What is the expected lifespan of those 16x2 character LCD?
My experience is that the 1602 type LCD display module will last a long time. What will not last a long time is the backlight if your module has one. In particular the ones I've used that have a white LED backlight last about 3 years before the LED brightness dims to the level as to render the display to about 10% of its original light level. 

It is possible that other types of backlight may be better. A yellow/green type of LED may last a lot longer. On the other hand displays with EL strip backlights are also known to age in fairly short order.