Fresh yeast question..

time/temp

amount of yeast

concentration of live yeast cells

I've seen a lot of mumbo-jumbo about yeast, and it's really not all that complicated:  when we add yeast to a dough - no matter whether it's fresh or dry - what we're doing is artificially inoculating the dough with a "starter culture" that can be either commercial or wild, i.e., sourdough starter.

Fermenting dough to double or triple volume is simply a matter of letting the yeast do its work of reproducing, digesting sugars and excreting CO2. When the yeast population has reached a certain level of concentration and activity, the dough will have reached its desired volume.

Time/temp: Obviously, the longer a dough ferments, the longer the yeast will have to do its thing, and since it's more active at higher temps, the higher the temperature of the dough, the less time needed to reach that desired volume.

Amount: Let's assume yeast reproduces at a fairly constant rate - say, doubling every 10 minutes - and you need (pick a number) 100 million yeast cells at X temp to produce your desired volume, the greater the number of yeast cells you introduce into the dough, the fewer doublings, and therefore, less time, it will take to reach that 100 million target.

Freshness: This is really a subset of amount, since the older the yeast, the lower its potency, i.e., the proportion of live cells to dead ones. The fresher the yeast, the greater the number of viable cells and the less time to reach your fermentation target.

I think the most important thing to remember about yeast in general is that there's nothing mystical about it: yeast is a single-celled fungus that eats sugar and farts CO2, and over milennia, humans have learned how to domesticate it, culture it and use it to inoculate all manner of fermentation products, from bread, to beer, to wine.

So the short answer to your question is: it depends ...

As far as the oven preheat, I find it generally works best for me if I start my preheat at the same time I set my breads/rolls aside to proof.  I'd rather have the oven sit at temp for an extra 10 or 15 minutes than have to deal with overproofed products that look like tired, deflated balloons. Even the most robust yeast can't do its thing after all the sugar's been consumed.

Stan Ginsberg
www.nybakers.com

Let me be so honest as to say that's the trap with baking by the clock.  One has to watch the dough carefully esp. when changing something major like the yeast.  Sounds like the fresh yeast was very fresh!  (Lovely!)  Try using less fresh yeast until it fits your schedule.   

I get all kinds of panic feelings at short rises.  I don't like them at all.  I've seen the beauty in long ferments both on my digestive system and taste buds and cringe at the thought of an hour bulk rise let alone 20 minutes.  Yikes!  "Oh, what a world, what a world!"

I do remember rise/proof times being less with FRESH vs DRY yeast.. Is that right?

I've never heard that before, and I'm rather suspicious of it.

For one thing, it seems to assume a very particular "conversion" of amounts. Is the "right" conversion 1/4, or 1/3, or 1/2, or ...; by weight measures or by volume measures? (By choosing a particular conversion factor, you can "make" it true  ...but that's not fair.) Also, are the different yeasts the same age (i.e. equally "partially dead")?

Perhaps what was meant is FRESH yeast starts working immediately, whereas ACTIVE DRY yeast that's not pre-dissolved takes a little while to "wake up". That's not true at all with active dry that you dissolve in warm water so it's already woken up, and it's insignificant with the newfangled INSTANT yeast that wakes up so quickly you hardly notice.

If your experience was your FRESH yeast worked almost too well, try using less of it next time. (And in any case, as dmsnyder says, "watch the dough not the clock":-)