[richardt]

We seem to be in a period of change with respect to the concept of keeping beer on the yeast in Primary Fermentation vessels.

Many of us read the books and magazines.  Many of them say "rack to secondary after 7 days." 
Even CP's books seem to say that.  Keep in mind when they were written.  It was right, then.

Now, as Major says, it seems that there's a difference between homebrewing in buckets or carboys (5 or 10 gallon batches) and brewing in massive SS conicals that have additional issues (e.g., turn-around-time, CO2 pressure and Weight) that we homebrewers do not.

The homebrew vets and the recent science support the notion that we homebrewers are gonna be just fine leaving the beers on the yeast for a month or so without deleterious effects, regardless of beer style.

Bottom line:  you can have a life--if family duties arise, you can let the beer wait a day, or a week, or a few weeks, without having to worry.  To borrow a cliche:  It'll all be good!

[bluesman]

If you need to keep the beer on the yeast for more than three weeks the beer should be chilled down to <40F to preserve the yeast and prevent any potential autolysis. I have kept beers on the yeast for 4-5 weeks @ 65F without detriment to my beer. It is recommended by the yeast manufacturers to keep yeast refrigerated to prevent autolysis and other ill effects that can be caused by warm storage. How long is too long...? That's a question I answer by saying "better be safe than be sorry". 

[skyler]

Not sure if it was autolysis, but the only beer I hated in recent memory was one where I overpitched and left it on the yeast for 6 weeks. I think a month is as long as I would let it go. As to secondary - I do them when it is more convenient to do them (like when I need a free primary vessel, but am not ready to keg). I do believe many beers benefit from a couple weeks of lagering in secondary, but the added risks are good enough reason not to bother.

[alikocho]

I don't worry about autolysis, and the bulk of my primaries run for 10 days or before bottling. Let it ferment, let the yeast clean up and settle. Don't worry about it.

And as someone said, this seems to have been a concern 10+ years ago, but todays yeasts aren't so tricky.