Personally, I like fairly short dungeons in Zelda games, but lots of them. This is because I usually can't play for too long at one time, not like I used to when I was younger and had loads of free time on my hands. When I save and start the game up again, I'm at the entrance to the dungeon (in most Zelda games, this is the case), so that usually means that I have to go through a few rooms to get back to where I left off. Furthermore, if the dungeon is too big it might be a little hard to remember where I was last, though I doubt you'll make a dungeon massive enough for that to be much of a problem.
A good thing to do is to ALWAYS make the boss room fairly close/quick to access from the dungeon entrance, no matter how small or large a dungeon is (unless it's some kind of mini dungeon). That is especially important if you won't have quick saving or some way to save exactly where you left off. Another thing you might notice about Zelda games is that they tend to make previously ventured dungeon rooms a lot easier/quicker to navigate after you get the dungeon item, which is a neat little dungeon design trick to make backtracking not seem so boring or tedious to the player, but that's just part of good dungeon design, and it only works if you plan to follow the same system (i.e. getting an item mid-way through that is required to reach the end of the dungeon and will most-likely be required on the boss to win); if you don't design a dungeon to work like that then it obviously doesn't work, but you can do it on a much smaller scale with keys unlocking doors, or buttons that open up previously locked doors to open up shortcuts - stuff like that.
If you design a dungeon well using tricks like those, then you can have a much larger dungeon and still make people like me fairly happy as well as people that love really lengthy dungeons. Though I do still stand by shorter dungeons, but lots of them.
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Btw, I totally forgot about testing your demo until now. Do you still need any help testing? The latest I have is the "Zelda 0.14.13" test demo and I see you now have a demo 15 out, so I think I got a little out of the loop from being gone, but I'm healed up a lot now and I'm active again so I can help out a bit if needed. In addition to testing, I can easily record high quality and smooth gameplay. I could even put together a simple trailer if you ever need it. Or, if you don't have your own good recording software and you are looking to purchase a good one, then you can get Bandicam, which is what I use to record. There is another good one called PlayClaw, and it may even be better for you if you want all that third-party stuff and the various overlays. Both of those programs are far superior to Fraps, and all 3 are just under $40.
Guess I could've sent that last part as a PM, but I was already posting a reply... guess I'm a little lazy atm.