Motorola V710 (Unlocked)

Well let me start at the beginning, around 5 years ago I purchased the V710 new for around $300. about 4 months later I was riding my motorcycle down the road aprox. 40 MPH when the phone fell out of my pocket and hit the pavement sliding for about 40 feet before it came to rest. I turned around and found that the battery and battery cover had came off. I picked it up put it back together and found nothing to be wrong except for some road rash. Later that summer I was caught in a rainstorm and got soaked. the phone started flashing and doing weird things when turning it on. After drying out for a day it started working with no problems. My job environment has not been very nice to this unit also, since I,m involved everyday with machining and grinding. The grinding dust finds its way to the speaker magnet and starts distorting my sounds. This happens a lot. Over the past several years I have purchased used V710 phones very cheep for parts. I have replaced the outside plastic case 2 times, the speaker 6 times, and the battery only once in five years. However the insides are still original, and works just like the day I purchased it. This phone also will make and receive calls in hard to reach areas when others will not.
Just how much longer will this phone last??