Beersmith - I have lost temp, too on occasion, but I can direct fire to maintain temp in my MLT. Others will drain off to a prewarmed cooler to hold temp on the wort that is not being decocted. One fellow brewer swears that decoction is the key to the "true" Munich Helles flavor profile. He never uses Melanoiden malt.
As to longer boils, I don't think that boiling beyond 90 minutes (to drive off SMM) is necessary, but it may give you a better chance at higher amounts of Maillard reactions. I haven't done so, but iwould like to hear the comments of others.
Browning reactions: Also known as Maillard reactions, browning reactions is the term used to describe the chemical change that occurs when a sugar solution is heated. The chemistry of the reaction begins when amino acids (liberated during mashing) and reducing sugars combine under heat to produce melanoidins, which add color and body to beer. These reactions occur during the malting process of some grains as well as in the kettle and can be very beneficial in some styles, such as Bock beers. Flavors associated with melanoidins include toffy, nutty, malty, and biscuity.
EDIT: i dont rule out a decoction schedule can do this ^^^^^.
I often wonder if either on our scale of brewing, or because there's a very precise method for achieving this, that it can be difficult to replicate what breweries perform. I may run experiment soon, taking my melanoidin and about a pound of the base malt (pils for instance) and withhold that. then boil it, mash in, and add that to the entire single infusion mash. perhaps additional melanoidins will be created and into the kettle for increased maillard reactions to occur.