If you are using the park position of the transmission to hold the car parked on an incline, have you ever noticed how hard you have to pull on the shift lever to get out of park? That's because everything is bound up and under a load it was never designed for. You can/will given enough time damage the transmission case, the pin,the parking pawl, the shift cable, etc. etc. Plus with the brake on it can never come out of gear and roll freely down a hill until it crashes. Lots and Lots of people never have a problem. Lots of people smoke, drink, etc.etc. and never have a problem. So pick your gambles. If I remember correctly from 50 years ago or so teachings, the parking pawl was originally designed to keep the transmission stationary from a start so you weren't doing a neutral drop everytime you started the car and then put it into gear. Also transmissions are not all the same and there are millions of different designs. Best bet fix your E brake and use it regularly to keep it working, but you PROBABLY will never have a problem either way.