That's what I do. As long as you filter each time, you shouldn't have a problem. Of course, you're getting this advice from someone who applies a less-than-pristine varnish finish to his boats.

Ross

: I just applied the first coat of Flagship varnish to my hull. I carefully
: poured about 10 oz. of varnish from the new can through a strainer into a
: clean plastic container and used a foam brush. Everything went fine. After
: finishing, I had about 5 or 6 oz. left in the container. My first instinct
: was to discard it, but at 28.95 per quart I couldn't bring myself to do it
: - back in the can it went. Did I just doom the finish on my boat for the
: sake of 5 bucks worth of varnish?

: Jim