Hammers have to be eventually replaced, as well as other parts of the piano. An instrument won't go on forever without maintenance and replacement of worn out parts. As much as one may wish to believe, instruments do age. IMO, frequent left pedal use is a non-issue.
If the hammers need to be replaced after 8 years, then so be it - you got 8 years worth of playing with them. That has much more lasting value then a set of hammers. It is an unlikely scenario though for a home instrument to have hammers last only 8 years, unless you are an exceptionally heavy player. Institutional instruments that get bashed 24/7 have much more frequent need for repairs. Even on such school instruments I have rarely encountered a left pedal that does not do its job.
If you do a few simple things such as: not using the left pedal as a substitute for a practice pedal and not playing forte with the left pedal, wearing out the hammers due to left pedal use should be no issue at all.