I personally do the same when playing the Legend of Zelda games (or any game in general), but i decided to time myself for the fact that ive played the game multiple times to begin with and it seemed something worth trying. Try it! It'll give a new feeling of accomplishment. x]
Well after playing through the game dozens of times over the last 13 years, it wasn't until a couple of months ago that I sat down and timed myself.
I looked up the optimum route for a glitch-free run on speedrunwiki.com (Fire, Forest, Water, Shadow/Spirit) and learned how to get through the haunted wasteland without the lens of truth among other smaller tricks.
Timing from when Link jumped out of bed to the final blow on Ganon I finished in 5 hours and 57 minutes. I was very happy because my goal was under 6 hours.
I actually could have done much better because I screwed up big time in 3 places. The best one was that going from Kokiri Forest to Hyrule Castle for the first time, I was backwalking and missed the bridge and fell into the water. And the best part is that night fell seconds later so I had to wait for a few minutes to carry on. I also died fighting Bongo Bongo (it's a long way back to the boss room) and failed to pull off a time saving trick in the Water Temple. Also a week or two later I found out about another trick that would have saved me a minute or two as well.
Well... TECHNICALLY my record for 3 Heart Challenge is 29 hours, according to my Wii (since I played the Virtual Console version), but I left the game running for most of the day without playing it. In reality, it's probably somewhere around 15.
...Okay, I'm going to replay it now, because my record is awful. I guarantee I can complete it quicker - this time, I just won't get the Biggoron Sword or the bottles, because those took a lot of time. XD
The one time that I played it from start to finish without stopping it took around 8 hours. I wasn't doing a speedrun or anything. I was just playing like I normally do, so I'm sure I could've done it faster than that.
i like to take my time and enjoy it, not rush through it. last time i did it, just getting what i came across as i went along, i had 18 hearts by the time i faced Ganondorf and around 55 Gold Skulltulas. i don't get a lot of time to play games, probably an hour or so a week, so it tough to say how long it takes to complete a game
It would take 8 to 10 hour for me to completely to the game from beginning to the ganon battle.
(Deku Tree - Jabu Jabu's Belly) ~ 1 to 1 and half hours
(Forest Temple - Fire Temple) ~ 1 and half hours
(Water Temple to Spirit Temple) ~ 2 hours
(Barriers and Ganon) ~ 1 and half hours
= 6.5 to 7.5 hours in total.