Answer: Sago palms usually grow 10-12 feet high and about 10 feet wide at maturity. They are rather slow growing, so I wouldn't expect them to reach maturity for at least a decade. The plants will eventually grow a trunk with only a crown of fronds. You can cut the spent fronds off right at the trunk, but you cannot "top" the palm to reduce its height. Doing so will kill the crown, which will kill the entire plant. Sago palms develop deep roots which remain about as wide as the width of the canopy of fronds. I wouldn't plant the sagos closer than about 5 feet to the house, to allow plenty of room for frond development.
Best wishes with your landscape.
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