What are the downsides of using less yeast?

I am not a yeast expert but doesn't it replicate itself? Maybe I am totally wrong about that. Wednesday day I brewed my second batch and I pitched a half a canister WLP011 European ale yeast into my carboy. 24 hours later there was strong fermentation activity and less than 48 hours it was strong and frothy. My plan was to move it to a secondary fermentor today and pitch a full vial of yeast with a little honey. Yes I know 3-4 days is way to early to move it but I fly out of town for over a week tomorrow and my last batch with a full yeast pitch in the first stage did almost nothing after five days so I did another full yeast pitch in the second and it turned out to be an amazing ale. The reason I ask this question is that I am considering not moving the wort to a secondary fermentor and not picting the second yeast since there is still so much activity going on.
Can half a yeast vial fully ferment a strong wort over time?




Cheers

From what I understand, even if you have only a few cells of yeast it will ferment eventually. The risks are that wild yeast or bacteria will take hold first and change or ruin the beer. Also if you pitch too little yeast they get stressed while building up to cell counts needed to ferment the wort. This can create off flavors in the finished beer. Also it is widely accepted that a vial or smackpack of yeast do not contain enough yeast cells to optimally ferment a 5 gallon batch in all but the lowest gravities. IMO, always make a starter when using liquid yeast unless making 3 gallons or less.

Here's my advise:

Have a safe trip and relax and let things go. You'll return home to a nicely fermented homebrew worthy of sharing with friends and family.

Begin2Brew said:

Here's my advise:

Have a safe trip and relax and let things go. You'll return home to a nicely fermented homebrew worthy of sharing with friends and family.

Click to expand...

^^this^^

To answer though: proper pitch rate will create a healthier fermentation with no stress on the yeast and less chance of developing off flavors assuming you also ferment at proper temps