Average lifespan

I've been researching different hair system types and adhesion methods and have located a stylist in Toronto that I want to install the system. I have yet to decide on which type of system (lace or poly), but I'm definitely going with Lordhair (that's the only brand the stylist will work with).

However, I'm still nervous to pull the trigger because I'm not too sure what the annual cost will end up being. One thing I'm not sure of is how long I can expect the system to last. I do workout, but work indoors so I don't have much exposure to sun.

What is the average lifespan of a system?

Any input would be greatly appreciated!