337D : Gear extension took "forever" out of Annual

[B2C2]

I have found that for my mechanic, the hydraulic mule that they use for gear swing checks sucks hydraulic fluid out of the system when they shut it down. I always check that they have topped the fluid after they do this, as I had the same experience you did with slow gear action after annual when they first started doing this and check showed low fluid level. You said you topped the fluid, but I would check it again and perhaps drain and fill in case there is air trapped in the system somewhere.