Daily duties? Basically it depends on your role, if you are a programmer, definitely you are going to program, if you are a system analyst, you have to think and therefore design the flow of the program.
How long? It depends on the project how long it will take, some projects take about 3 months or more.
Opinion? I think it's okay to be knowledgeable of Java language but at the same time you should be open with any other languages that are arising nowadays. With Java language, it gives the programmer a chance to incorporate their programs with other languages.. such as XML, etc.
Regards,
Ronron