I started out building a Long-ez so I built a 12x4 with TGIs and MDF top. I cut it down to 8x4 and still have the original MDF top. I did like Larry above, every once and a while filled in sanded and rolled some white paint (whatever I had ) . Make sure you have an overhang around the perimeter.
When I started a new project, I rolled out some Ram board (comes in a roll from your fav box store). Tape the perimeter and you have a pristine working surface for panel work, finish assembly of parts etc.
My 4x4 corner posts have leveling but no castors. This is my main work table.
I have two EAA tables for my power tools and misc. projects that temporarily get put aside and worked on.
I personally like a really nice work bench. It has served me well.
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