I've had mine for nearly 50 years, and it is still my preferred process timer. I do check it from time to time - having your clock drift without being aware of it can mess things up.
I have a newer three-button one from when Smiths/English Clock Systems merged with Time Controls. That design needs a periodic clean - it does not like a damp atmosphere (!), and some of the moving parts start to bind. The buttons are not as good - you have to Stop, Reset, Start - and they are not as easy to hit as the levers.
Those cream ones were the standby in the physics lab when I was in school. I figured if they could take that abuse, I would be fine with one.