As most said ...
I would add..
If employees You want leave after 6-8-10 years,
(so they are skilled and experienced, no ?),
who have been doing satisfactory work,
(as otherwise they would have been replaced, no ?)
You are probably not paying enough.
My 0.02€.
Find a way to pay them more, like extra hours or incentive programs linked to work profits.
If everyone else also wants the incentive programs, tell them Hell Yes.
10% extra work hours and 10% more productivity per person will probably increase your total *net* profits by 20-50%.
Give the employees say half of the extra profit.
Watch productivity soar,
net profits soar,
and morale increase unbelievably.
You could probably increase net profits by 1500$/p/ month, and give the workers 800$.
x 6 ==> 4200$ extra net per month for you.