Question
I have 4 large ( 10 ft. tall & 8 ft diameter) which are probably about 20 years old.  They no longer suit the purpose of where they were planted.  They are attractive trees with a nice yellowish sheen to them.  Are they worth saving and transplanting or are they near the end of their lifespan?

Answer
They can be moved but this maybe a large job.

Evergreens should be moved earlier in the fall than deciduous plants so they have time to form new roots. They need at least 6 weeks before the ground freezes. In the spring, Evergreens can be planted up to 4 weeks after deciduous trees have opened their leaves, providing that the newly planted trees receive adequate water.

When you want to dig up a tree or shrub for transplanting, retain as much of the root system as possible. All ages of evergreens, can be successfully moved only if a ball of soil is left around the roots. The exposed roots should be protected with moist burlap or newspaper or with polyethylene sheeting. Every effort should be made to reduce root exposure to wind and sun, keeping the ball as moist as possible. It's best to prepare the hole before digging up the tree you wish to move.

Size of the root ball and size of the hole:

For deciduous trees and shrubs the soil ball should be:

Width = 9-12 in. in diameter/every 1 in. of tree diameter
Depth = 6 in./every 1 in. of tree diameter

For example: A tree trunk 2 inches wide would need a soil ball of 18-24 inches wide and 12 inches deep.

Dig the new hole twice the size of the rootball and as deep and fill with good top soil or potting soil. Mulch around the tree with not more than 3 inches deep of organic mulch not piled up on the trunk.

This maybe too large for you to move but there are professionals that use a tree spade to dig and remove trees. Here is the web link to dealers of one of these spades called a vermeer tree spade. Click on the dealer location for a dealer in your area.  http://www.vermeer.com/vcom/EnvironmentalEquipment/Line.jsp?PrdlnID=3840