No good reason to wear out a set of tires that you don't like. They aren't that expensive. I would upgrade and keep the old tires - many uses for them. I felt like a sad sack once when I had to go the bike shop and ask for a replacement for my blown out tire. They didn't care, but I felt small for admitting that I didn't bother to keep any spares on hand. Also, what if the shop was closed?

Also interesting that you use the word "upgrade". Perhaps an upgrade, but tire width is certainly debatable.