Recurring Problem With Air Conditioning

Hello All,
I have a ten year old Taurus. The first seven years the AC was like new, but after that I've had repair done for the last three summers (leak sealing procedure and cooling agent replaced). It's happening
again this summer. I used it three or four times and it's only slightly cool.
What can be done? Can this AC be restored to new? Is it normal to need repair every summer?
Joek In Jersey

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