SEPDA,
CONGRATS and welcome to CAL. I sat and will sit reserve for Dec and Jan in EWR. PM if you have any more questions or post them here to help others if you like.
TO clarify the seat lock...you can bid up at anytime. This means bid to a better position. You can bid from 737 to the 777 as a FO and then bid back to any of the aircraft as a CA. This is when you incur the 2 yr set lock.
I am 737 so I can't answer the 756 stuff but I hear the Sr. guys go to Europe and etc...(good trips) while the Jr. guys go to less desirable places. However, most flight leave in the evening and return a day or so later in the morning which makes them more commutable than the 737. If you are going to live within 2 hrs of EWR, you will be money. I have a friend who has 1.5 yrs with the company and is at 40% on the 756 out of EWR.
Hope this helps.