You already received great info on feeding so I won't address that. You did ask about their personality and I'll attest that they're wonderful birds. So curious and friendly. I had three adults birds that I bought at about age 3. Two have since died but this spring I got a new ISA Brown chick (also from Townline, incidentally).
The one thing that I've read, and which I also experienced, was a tendency for eggshells to thin to the point that they break even with the gentlest handling. This happens with the older birds, sometime after 2 years. I tried increasing oyster shell and that had minimal effect. Then, I switched from Purina Layena pellets to a mash from a local feed mill and that has really helped. I'm not sure why but am guessing that the Purina has probably sat around for months and the local feed mill mash is fresh so the nutrients are fresher? Totally guessing here.
My own remaining adult bird, who is probably about 4 has nearly stopped laying altogether. I'm not sure how this compares to other breeds but I do know that the hyper laying breeds do seem to burn out faster. But, while they're laying you get tons of huge eggs from really fun birds. Enjoy!