Instead, reward them economically. Everytime the company takes a leap forward, make clear to them that they were important for the process, and share some profit.
And make clear that being important in a moment doesn't automatically mean they will be important in the future: they will have to compete on results, like everyone else.
Some people have 5 years of experience and some people have 1 year of experience 5 times.
Thus I'd give the previous poster some leeway too, and read their (but also your message) as: there is an implied basis of skill and value you expect early employees to continue bringing to the table, but when that is satisfied, reward their loyalty too (either with promotions or money or status or stock or...).