100%. 20 Years of service means you will have saved so much money and time in replacing them with other staff potentially every few years. Not only that 20 years of loyalty these days means alot. I would reward my employee with some kind of lifetime bonus. Maybe a one off payment of a couple grand, or just increase their wages to reflect the years of service etc.
Obviously in a modern world you don't need to do any of this, but personally from a moral standpoint i would feel like they have more than earned it.