After doing many lagers, I feel strongly that the best results come from pitching a HUGE starter at slightly under optimum fermentation temperature. I'll pitch the yeast at 46 degrees into my 48 degree wort and allow the temperature to rise to 50 degrees.
The reason the yeast package says to pitch warm is to compensate for the gross underpitching of the yeast, not to make the best lager!
I don't pitch my ales at 90 degrees and then turn down to 70, and I don't pitch my lagers 20 degrees too warm either. There are several reasons- one is it is hard to "catch" the fermentation at the right time. You want yeast reproduction but not fermentation. Also, there are flavors produced during that reproduction/beginning of fermentation that you don't want in your beer. Another issue is dropping the temperature- it takes a LONG time for fermenting beer to drop 15 degrees! Most of the actual fermentation could be over before you ever get to 50 degrees.
The primary fermentation time period usually lasts 10-14 days, and that's at 48-52 degrees usually (depending on yeast strain). After that, the diacetyl rest is done (if doing) and the beer is racked and the lagering process begun.
I like to lager at 34 degrees for one week for each 8-10 points of OG. (That's from George Fix). So, for a 1.060 OG beer, I'll lager 6-8 weeks. I drop the temperature slowly, for diacetyl rest temperatures to 34 degrees, usually 5 degrees per day.