Hi Ian
When introducing any new birds into your flock, you are best to isolate them in a seperate hen house for 7-10 days. Hybrids tend to live for around 4 years, depending on the birds background i.e. ex batts, barn reared, organic free range etc.. but also how they are treated, what food they eat and general well being. I have 80 ex batts which I have bought over the last few years, some died at age 2 some are still going aged 4. I also have 1 old silkie cross cockerel who is 12 years of age!
Regards Sue