Change default settings in LTM configuration

IMHO the proper way is to keep the default profiles, add you own profiles (use default profiles as parent) and change the values. Then apply the profiles to your objects. E.g. create a new TCP profile called my-tcp-30s, use tcp as parent and change the timeout to 30s. Apply the profile to your virtual server.

Personally I would create new custom profiles with settings as required and then use those as the parent for any further profiles.

Thanks for your answer, I choose a bad example I'm sorry.

My request is global, I would like to change the default value for a lot of parameters in a BigIp, a better example : when I create a new Pool or VS I would like to have my defaults values and not the bigip defaults values. For example when I create a new VS I would like to have "my_http_profile" by default and not "none" for all my new VS.

Thanks

depending on your standards/complexity/number of services you might use iApps in that case. Here you can define defaults for your services. But they do only apply to the services you added via iApps.