Generally speaking, my roster has been fairly stable. Flying about 55 hours/month, with perhaps 8-10 hours/month on average. No paxing in April, DXB-SIN in May and BRU-LHR-SIN in June.
As for "bidding system", there isn't one. As has been pointed out, Cargo tends to get the "leftovers". The SYD/LHR based get the most productive COPs with the 744 pax fleet getting their pick after that.
It really depends on your outlook if Cargo is good for you. Personally, I don't want to fly 80 hours/month. I enjoy being off 12-14 days/month. I, don't want multiple legs/day, as it is the SIN-MFM-ICN day is a killer.
Travel benefits suck...but I knew that when I joined. The only thing I object to was the change for the home base ticket. It used to be good system wide, but the last contract change about a year ago changed that. We do have unlimited ID75 with other airlines, but it's expensive and SA. A confirmed ticket is worth it and cheaper. At a previous airline, we had ID 90 agreements and ZED fares, but it's all SA. If you went to get someplace, having a confirmed seat is the way to go.
If anyone wants more info PM me.
Cheers