Boeing MD-11 (D-ALCH)

I really love the MD-11 along with Lufthansa and FedEx as well, but why dont these carriers using them convert some of the 747 and 777 into cargo planes that they are retiring at a fast pace? that will also last a long time. I assume it is getting very expensive to maintain these as well. Arent they gas guzzlers compared to 777/747 that can be converted? I know Lufthansa is now into 747-8 for cargo, but why are they keeping these? I assume because of the older technology/engines etc, that they will just run forever maybe....

No 747-8 Cargos are inn the Lufthansa fleet, only 11s and Triples

Answering bigkahuna400, whether to reconfigure 747's et cetera to cargo mostly has to with the economics of fuel burn/efficiency.
It's a quite fascinating spreadsheet operation with the other cost factors itemized out over several years.
I personally feel that keeping 747s in the air because of their "extreme physical attractivity" to pilots and most aviation fans is a gut-feeling factor.
I'd personally love to have a retired or airworthy 744 et cetera in my backyard if I had the means.
Just think about John Travolta's 707 and Tom Cruise's P-51 Mustang!
Now, back to reality at 0325 local.