You can use multiple custom services and characteristics. To estimate the maximum number of services and characteristics which we can declare, is not straight forward because it will depend on the BLE stack GATT Database memory.
Please refer this document -> http://www.cypress.com/file/140826/download for Generating Custom UUID.
Thanks for your answers, sorry for my let answer..
To my first question it's more to know how it's usually made, than estimate the max number possible (my question was no clear about that). Does it have a notable influence of the time make by a phone for discovery for exemple ? Just to know if it is best suited to use 2 big large characteristics or 100 characteritics for example? Fact that most of the exemples just use a few ones.
About the document it's still not clear for me
Is is ok to generate a different random UUID for each caracteritistics or service, or just generate random base UUID and make a logic organization with the rest of the UUID ?
There ise different UUID generators which one does i have to use ?