ATR type rating
I cant give you any info on the 777 or 747 type rating. However, the type rating for the ATR 42 lasted for 4 and a half weeks. One week systems, one week performance and two weeks in the simulator followed by a session of six circuits. The two weeks of ground school covered similar stuff done in the ATPL's but it was specific to the type. The two written exams were not as challenging as any of the ATPL's. The whole course was covered at a fairly slow pace and was a lot of fun. I believe there is a six week course for those that havent done an MCC course but I am not too sure about that! Good luck with the rest of your training.
Bradley