2 vials at once or space them out?

If you're just trying to use them, I'd say pitch both first. Otherwise pitch one vial, take a hydrometer reading to see if it's near range after a week, and pitch the second if it's really slow going.

 

Pitch one, apply heat, sit back and enjoy the ride.

 

Pitch both.

 

One vial is plenty for a 4.5% ABV beer.

Just be patient with WLP565 and chances are everything will go well. Do you have the ability to get the fermenter hot (> 80°F) over time? That will benefit this yeast/fermentation.

Cheers!

 

Depending on the age of the yeast, you might need/want both vials. But pitch them at the same time. And heat will speed up the fermentation, but it is possible to ferment with this starin at more moderate temps. Patience is key.

 

Like Jack said pitch only one vial. If your yeast floc's out too quickly you can rouse the yeast after a week.

 

You will be fine with pitching one vial of that yeast at that OG. I've fermented it in the 60's with one vial and a higher OG and the beer came out amazing.

 

Wow, lots of different opinions. To me, it seems fairly straightforward that you would pitch both: the first stage of fermentation is in many ways the most important, and you want plenty of healthy yeast onhand. You can always buy another vial and add it later if need be.

 

That's true. You want plenty of healthy yeast. But you don't want too much more than plenty. Although overpitching is generally considered safer than underpitching, it can be taken too far. But whether or not 1 vial is plenty depends on the pitch rate you want and on the viability of the yeast (a function of age, among other things).

 

If you have bought two and won't be making two different beers, I say pitch them both at the same time.

 

Pitch one, you can always save the other one and boost it back up with a starter if it starts getting old (6+ weeks)