I'm a "fierce" proponent of adjustable height work surfaces, especially for assembly and suggest that if you can accommodate that, you will be very well served over time. It's easier on your back and more efficient for the task. Knock-down supports can provide a lot of flexibility in various heights and they can be extremely simple, such as mere "X"-es with interlocking joints. When not in use, they can hang on the wall or slip into a rack.
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The most expensive tool is the one you buy "cheaply" and often...