Short term storage of bechamel How far in advance can I make a bechamel sauce before using it without having to cool, refrigerate and reheat.

For instance if I'm making a creamed spinach dish for a dinner party can I make the sauce right before my guests arrive, leave it on very low heat or in a warm oven unattended while I visit with everyone before dinner, and then assemble the final dish an hour later? How long could I push the timing? Also should I leave the sauce in a heated environment, or just on the counter and then rewarm it? Will there be a noticeable drop in quality?
You could make it beforehand, store it in the fridge, and warm it up in the microwave when you want it. You'll only get problems if you add cream - then it may split.

It really is not worth the risks of having it sitting around. The alternative is to have your roux prepared, and work the sauce up quickly.