Yes, all the time, if there is one available. Hell, the first thing I do when I start most games is google for ‘{game title} ??’ or ‘{game title} site:foolmaker.net’.
I don’t know in advance if a game is going to be convoluted and horrible, with a crazy annoying branching structure, or is going to have ‘perfect’ branching like in Haru no Ashioto (with pretty much the minimum number of options) or even more of an extreme like in Colourful Box where you pick your route in advance.
However, if I do have to spend time replaying to try and get on a route, that’s time I’m not actually playing the game. If I’m reloading and skipping, trying different sets of choices to see if they get me past a particularly annoying bad end (e.g. Soul Link or Extravaganza) I’m not getting anything extra out of the game - just wasting time. When the average eroge takes 20+ hours to complete, with some taking much more, you don’t really have time to waste when playing these games!
So, yes, rather than even run the RISK of wasting time, I jump straight to the walkthrough.
Hell, and for the couple which don’t have walkthroughs available, I often find another way to do it - G-Senjou no Maou I got pretty much immediately before any walkthroughs went up. I pulled out the script and grepped it for branch points to determine what I had to do.