Hello Dave,
Ordinarily I'd say you would likely end up going crazy from hearing yourself say CQ a thousand times without an answer. Not sure though with the higher bands being shutdown like they often are now, but still think you wouldn't get many responses. I'll settle with the answer of if you are into the "fun" factor more than the possibility of wall paper then don't bother with 80 during the day. If you're hoping for something else to add to your already formidable collection of plaques and certificates then you have to try for q's in daylight hours.
That advice comes from past experiences calling on 40 and 80 during the day with NS4 and NQ4. The station size or rarity of the prefix didn't seem to matter much. There just weren't very many answers during daylight hours. I (we) would pick up some q's, which sometimes is all the difference it takes to eek out a win, but the rates were down at the 5 to 10 an hour rate. Not much fun there. Again, maybe it will be better if the higher bands are poor that weekend. " Ya' pays your money and takes your choices."
There are literally thousands of unique prefixes so although a rare one helps, it isn't as strong a draw as you might think it is. I've borrowed WW4 and WX4 calls in some of the last few WPX's I've done but didn't see as much of a difference in score when I went back to my own N4 as I expected to.
Kevan